Fossils

["Group: OSTREIDA Subgroup: GRYPHAEIDAE Invertebrates | 101 Gryphaea Informal name: Devil\u2019s Toenail The heavy shell is composed mostly of Gryphaea arcuata calcite. The concave right valve fits like a (Lamarck); Lower lid within the larger left valve, which has Lias; Early a narrow, inrolled beak. Internally, the Jurassic; UK. single muscle scar is circular; the adult hinge has no teeth. Two left valves HABITAT Gryphaea lived on muddy sea beds, originally cemented to a Occurrence: small particle of rock by its tip. REMARK The coiled shell, adapted for living in soft sediment, is popularly called the Devil\u2019s Toenail. inrolled beak Typical length coarse growth 7cm (23\u20444in) ridges Range: Late Triassic\u2013Late Jurassic Distribution: Worldwide Group: OSTREIDA Subgroup: GRYPHAEIDAE Informal name: Oyster Exogyra Left valve, top view Both valves grow spirally. The left valve is inflated and rather weakly ribbed, with the beak coiled off to one side. The flattened right valve is ornamented by concentric frills. The left valve hinge has two groups of ridges below the beak. HABITAT Exogyra lived concentric frills beak cemented to solid objects in warm seas. Left valve, side view Exogyra africana (Lamarck); Late Cretaceous; Algeria. Typical length 5cm (2in) Right valve Occurrence: Range: Late Cretaceous Distribution: Worldwide","102 | Invertebrates Subgroup: OSTREIDAE Informal name: Oyster Group: OSTREIDA large ligament pit Ostrea Ostrea has a rounded shell, with a large ligament pit on the hinge, below the beak. The single muscle scar is kidney-shaped. HABITAT The oyster lives in marine or estuarine waters. The young often cement themselves to older molluscs, eventually forming a reef of variably shaped shells. Typical length Ostrea growth ridges 12cm (43\u20444in) compressirostra Occurrence: (Say); Chesapeake Group; Miocene; USA. Range: Cretaceous\u2013Recent Distribution: Worldwide Group: OSTREIDA Subgroup: OSTREIDAE Informal name: Cockscomb oyster Rastellum Paired valves The narrow valves of the tubular-shaped shell are composed of many sharp ridges divided by deep, sharp furrows. HABITAT This animal lived cemented by its attachment narrow beak to shell or coral in warm waters. area REMARK The vulnerable point where the valves meet is hidden, probably as a interlocking deep furrows defence against predators. zigzag margin Side Rastellum view (Arctostrea) carinatum, (Lamarck); Lower Chalk; Late Cretaceous; UK. Typical length 10cm (4in) Distribution: Worldwide sharp ridges Range: Middle Jurassic\u2013Late Cretaceous Occurrence:","Invertebrates | 103 Group: MODIOMORPHOIDA Subgroup: MODIOMORPHIDAE Informal name: False mussel Whiteavesia The triangularly ovate shell narrows towards the inconspicuous beak. The interior surface has ridges that appear on internal moulds and probably reflect fine external ornament. HABITAT A marine suspension feeder, it is likely that this genus was attached to the sea floor by byssus threads. REMARK This early genus may have given rise to the Mytiloids (see p.96) and the Unionoids (see p.104), although it does not show the iridescence present in those two groups. internal ridges limestone Whiteavesia matrix pholadiformis (Hall); Ordovician; Typical length 7cm (23\u20444in) Internal mould Canada. Range: Middle\u2013Late Ordovician Distribution: N. America Occurrence: Group: NUCULIDA Subgroup: NUCULIDAE Informal name: Nut clam Nucula serrated lip nacre concentric growth lines The small ovoid shells are lined by shiny nacre on the inner surfaces. There are two rows of interlocking hinge teeth separated by the ligament scar. The inner lips of the shell are lightly serrated; the outer shell is ornamented with fine radial lines and concentric ribs. HABITAT Nucula is a deposit feeder living partially buried in muddy sand. It inhabits both coastal marine and deep water environments. HABITAT The interlocking hinge teeth and the tough slippery nacre provide a defence against predation. Typical length 1.5cm (5\u20448in) hinge teeth Nucula gracilenta; Range: Cretaceous\u2013Recent Distribution: Worldwide S.V. Wood; Blackheath Formation; Early Eocene; UK. Occurrence:","104 | Invertebrates Group: UNIONOIDA Subgroup: UNIONIDAE Informal name: Freshwater mussel Unio Joined valves The oblong to ovate shell is rather smooth, with a bluish or purplish pearl interior. The middle ligament shell layer is prismatic and covered with a thin organic layer. There are two hinge coarse growth lines teeth situated in front of the beak, Occurrence: and two long teeth behind it. Informal name: Brooch clam HABITAT This animal lives in an upright Shells in position, partly embedded in the sands, sandstone silts, and gravels of lakes and rivers. Its larvae burrow under the scales of fish, but eroded beak drop off later, ensuring a wide dispersal. beak Typical length 8cm (31\u20448in) Unio menki (Koch & Dunker); Wealden Beds; Early Cretaceous; UK. Range: Triassic\u2013Recent Distribution: Worldwide Group: TRIGONIIDA Subgroup: MYOPHORELLOIDAE Mangyschlakella The thick valves of Mangyschlakella are semicircular, and each is divided into two parts: the main area, with obliquely concentric rows of tubercles, and the smaller posterior slope (the escutcheon), which is relatively smooth. Internally the shells are iridescent. Two corrugated and diverging teeth, suspended below the beak of the right valve, fit into sockets in the left valve. HABITAT This clam flourished in the shallow seas of the Mesozoic Era. tubercle rows Mangyschlakella elisae (Briart and Typical length 6cm (21\u20442in) Cornet); Bracquegnies Formation; Occurrence: Early Cretaceous; Belgium. Range: Early Cretaceous Distribution: Europe, western Asia","Group: LUCINDA Subgroup: LUCINIDAE Invertebrates | 105 Fimbria Informal name: Basket shell Fimbria has a tumid, ovate shell. The Fimbria subpectunculus ornament is netted, with stronger (d\u2019Orbigny); Calcaire concentric ridges at first, but then file-like, radial ribs that Grossier; Middle thicken at both ends of Eocene; France. the valve. The whole shell margin is netted crenulated on the ornament inside by a row of Occurrence: denticles. There are two main teeth below the beak, and two lateral teeth in each valve. HABITAT This suspension feeder lives in shallow, warm seas. concentric ridges Typical length 8cm (31\u20448in) Range: Middle Jurassic-Recent Distribution: Worldwide Group: VENEROIDEI Subgroup: CHAMIDAE Informal name: Jewel-box shell Chama spiral beak Chama calcarata Lamarck; Calcaire The left valve of this shell is thick and convex, cemented to the substrate Grossier; Middle by the spiral beak. The right valve Eocene; France. may show a fine microsculpture. Both valves have concentric frills, wide frills bearing fragile, grooved spines. grooved spine The hinge is degenerate, with one or two large, crudely shaped teeth, which interlock. HABITAT Chama inhabits sandy areas in warm, shallow seas, attached to rocks, corals, or shells. REMARK The spines attract the growth of algae and other animals, which then act as a form of camouflage. Typical length 3.5cm (13\u20448in) Range: Paleocene\u2013Recent Distribution: Tropics, Europe, N. America Occurrence:","106 | Invertebrates Group: CARDITIDA Subgroup: CARDITIDAE Informal name: False cockle Venericor denticles muscle scar The large, thick, oval to triangular shell has a prominent beak. When very young, it has narrow, radial ribs, which may be armed with small tubercles. These soon become smooth, flat ribbons separated by shallow grooves. In each valve the wide, triangular hinge plate bears three massive teeth. The inner shell margin is marked by a row of flat denticles. HABITAT Venericor lived in warm, beak hinge plate shallow waters, burrowing into the sand or silt. REMARK Paired valves in life position are found in large numbers in some strata. Venericor planicosta broad, flat ribs Typical length (Lamarck); Earnley 7.5cm (3in) Formation; Middle Eocene; UK. Range: Paleocene\u2013Eocene Distribution: Europe, N. America Occurrence: Group: CARDITIDA Subgroup: ASTARTIDAE Informal name: Astarte clam Neocrassina concentric Neocrassina ridges elegans The thick shell has regular concentric (J. de C. ridges. The hinge is thick, with three main Sowerby); teeth in the right valve and two in the left. Inferior Oolite; Middle HABITAT Neocrassina burrows into mud, Jurassic; UK. sand, or gravel offshore, to considerable depths. It is most characteristic of the Occurrence: Boreal and Arctic regions. REMARK Geologists regard it as a good indicator of cold conditions. Neocrassina shells in limestone Typical length Distribution: Worldwide 2cm (3\u20444in) Range: Jurassic\u2013Recent","Group: CARDITIDA Subgroup: CRASSATELLIDAE Invertebrates | 107 Bathytormus Informal name: Clam hole made The solid rectangular shell has two V-shaped by predator cardinal teeth in the left valve and one in the right, flanked by elongate lateral teeth. There Bathytormus are two muscle scars, which are joined by a lamellosus (Lamarck); roundly curved pallial line. The margins of Calcaire Grossier; the valves are finely crenulated. The young Middle Eocene; France. valves have strong concentric ridges. These fade out in some species but persist in others. HABITAT These clams were common in warm, shallow seas, where they burrowed into soft substrates. REMARK Some species of this genus evolved relatively rapidly. muscle scar lateral tooth Typical length cardinal teeth 2cm (3\u20444in) Occurrence: Range: Middle Cretaceous\u2013Miocene Distribution: Europe, N. America Informal name: Clam Group: CARDITIDA Subgroup: CARDINIIDAE irregular concentric bands Cardinia break Cardinia ovalis The valves of the shell of Cardinia (Stuchbury); Lower Lias; are ornamented with irregular, Early Jurassic; UK. concentric bands. There is a triangular area, which is Occurrence: angled inwards in front of the beak, deeply undercutting it. The lateral hinge teeth are thick and dominant. HABITAT This appears to have been a marine genus, burrowing into sands, silts, and muds in warm, shallow waters. Typical length Distribution: Worldwide 1.7cm (5\u20448in) Range: Late Triassic\u2013Early Jurassic","108 | Invertebrates Group: CARDIIDA Subgroup: CARDIIDAE Informal name: Cockle Acrosterigma A range of shell sizes Smooth, radial ribs separated by grooves ornament the elliptical shell. The hinge plate is well-developed small and sharply curved. In the middle of the lateral teeth hinge of the left valve are two small, diverging teeth, which meet one narrow tooth in the right valve. The front end of the hinge is extended to form one or two lateral teeth. On the other side is a raised place (the nymph) where the ligament is attached. The inside edges of both valves are sharply furrowed. HABITAT This creature burrows into the sands, silts, and muds of shallow tropical seas. Typical length 9cm (31\u20442in) Acrosterigma dalli Range: Late Oligocene\u2013Recent (Heilprin); Plio- grooves Pleistocene; USA. separating smooth ribs Left valve exterior Distribution: Worldwide Occurrence: Group: VENEROIDEI Subgroup: ARCTICIDAE Informal name: Iceland cockle Arctica beak Arctica umbonaria (Lamarck); The thick, smooth shell of Arctica is ovate Pliocene; Italy. to heart-shaped, with the beak turned towards the shorter anterior end. In growth each valve the hinge has three teeth lines below the beak, and a long lateral tooth behind. The hinge plate in Typical length front of the cardinal teeth is pitted 9cm (31\u20442in) and crenulated. Occurrence: HABITAT This cockle rests on both firm and muddy sand, from the intertidal zone down to considerable depths. REMARK The distribution of the genus indicates cold-water conditions. As fossils, they are regularly associated with other cold-water molluscs. Range: Late Cretaceous\u2013Recent Distribution: Europe, N. America","Group: VENEROIDEI Subgroup: CORBICULIDAE Invertebrates | 109 Polymesoda Informal name: Marsh clam Polymesoda has an oval shell, with Slab with weak concentric growth ridges shells and wrinkles. There are three cardinal teeth below the Polymesoda beak and strong, elongate convexa lateral teeth. Some fossils (Brongniart); still show radiating Bembridge Marls; colour bands. Oligocene; UK. HABITAT This clam lives in Occurrence: tidal marshes and brackish Informal name: Venus shell lagoons in tropical and sub-tropical regions. Lirophora ceramota REMARK European fossils (Gardner); Chipola differ from the American Formation; Early forms in details of the teeth Miocene, USA. and pallial line. worn concentric ornament growth ridges Typical length 4cm (11\u20442in) Range: Eocene\u2013Recent Distribution: Worldwide Group: VENEROIDEI Subgroup: VENERIDAE Lirophora concentric cords The ovate to triangular shell has its beak turned forwards. The valves are ornamented with concentric cords and radial threads and there are three diverging hinge teeth in each valve. Internally, the muscle scars are joined by the pallial line, which has a short embayment in front of the rear scar. HABITAT This clam burrows below the sand in shallow seas. Typical length 1.6cm (5\u20448in) Range: Oligocene\u2013Recent Distribution: N. & S. America, New Zealand Occurrence:","110 | Invertebrates Group: MYOIDA Subgroup: MYIDAE Informal name: River clam Potamomya wedge-shaped shell The shell is small and rather thin, varying from ovate to wedge-shaped. The surface is smooth, except where roughened by irregular growth lines. In the right valve, the ligament was attached to a central triangular projection; the rear part of this extends to form a narrow oblique tooth. The left valve hinge has a groove which receives this tooth. HABITAT Potamomya was often abundant in non-marine, silty sands and muds. Typical length Distribution: Europe ovate shell 1.5cm (5\u20448in) Potamomya plana Range: Late Eocene\u2013Early Oligocene (J. Sowerby); Headon Hill Formation; Late Eocene; UK. Occurrence: Group: HIATELLIDA Subgroup: HIATELLIDAE Informal name: Geoduck Panopea broad and Panopea glycimeris ridged beak (Born); Pliocene; ltaly. Coarse, irregular growth lines or, in some earlier species, regular concentric undulations, are visible on the valves of the thin shell. There is one small central tooth in the hinge of each valve, and a raised plate to which the ligament is attached. HABITAT Panopea burrows in silt and mud. concentric growth lines Typical length Distribution: Worldwide flattened 3.5cm (13\u20448in) posterior end Range: Early Cretaceous\u2013Recent Occurrence:","Invertebrates | 111 Group: PHOLADIDA Subgroup: PHOLADIDAE Informal name: Shipworm Teredina Cross-section of log Teredina was equipped with two small, inflated, triangular valves, cemented to a Detail tube. When young, the two valves gaped widely both at front and rear, but later a callum was secreted to cover the anterior gape. As the animal grew it enlarged its tube in stages. HABITAT With the use of its valves, this animal bored its way into wood submerged in fresh to brackish water. Teredina personata Distribution: Europe animals bore (Lamarck); London towards the middle Clay Formation; Early Eocene; UK. Occurrence: Overall length 5cm (2in) Range: Late Cretaceous\u2013Middle Miocene Group: PHOLADIDA Subgroup: TEREDINIDAE Informal name: Shipworm Teredo A fossil log in clay The shipworm Teredo has serrated, convex, T-shaped valves. The hinge is a long, slender protuberance to which the muscle is attached. HABITAT It lives gregariously in floating and sunken timber. Teredo cf. antenautae J. Sowerby; London, Clay Formation; Early Eocene; UK. tubes deviate to avoid others pyrite crystals small outer end Tube length infill containing pallets 10cm (4in) animals bore along Distribution: Worldwide Occurrence: grain of wood Range: Eocene\u2013Recent","112 | Invertebrates Subgroup: HIPPURITIDAE Informal name: Rudist Group: HIPPURITIDA Vaccinites Joined valves This genus belongs to an extraordinary group of lid-like complex bivalves known as rudists. One valve is conical upper valve in shape, enlarging rapidly from the base, where it is cemented to the substrate. The other valve is more or less flat, fitting like a small lid, with two long teeth descending from its inner surface, and two bosses where the muscles were attached. The outside of the cone is corrugated by longitudinal ribs. Internally, the walls are folded, forming vertical pillars, a narrow tooth, and sockets to receive the teeth in the other valve. The structure of the shell allows water to pass through. HABITAT Vaccinites lived near corals or on firm sand in warm seas. Although some species were solitary, others were gregarious and may have grouped together to form reefs. Typical length Vaccinites vesiculosus lower valve 10cm (4in) (Woodward); Late with vertical Cretaceous; Turkey. ribs attachment point Range: Late Cretaceous Distribution: Europe, N.E. Africa, USA, Asia Occurrence: Group: CARDIIDIA Subgroup: GRAMMYSIIDAE Informal name: False razor shell tapering Solenomorpha rear end The fairly long, narrow shell of Solenomorpha is widest near the front, where the beak is situated, but then tapers gently behind. The paired valves, which have a slight gape at the posterior end, are smooth, and have concentric growth lines. HABITAT Solenomorpha burrowed in soft sediments. Solenomorpha Internal mould minor (McCoy); Carboniferous Distribution: Worldwide Occurrence: Limestone; Early Carboniferous; UK. Typical length 1.8cm (3\/4in) Range: Early Devonian\u2013Late Permian","Group: PHOLADOMYOIDA Subgroup: PHOLADOMYIDAE Invertebrates | 113 Pholadomya Informal name: Paper clam This surface of the shell of Pholadomya is roughened radial ribs by numerous minute pustules. The radial ribs, crossed by weaker concentric ridges, are strongest in mid-valve. The hinge is thin, without teeth. The outer shell generally dissolves away, leaving a pearly film around the shell\u2019s internal mould. The interior is iridescent. HABITAT Pholadomya inhabited shallow seas, buried in sand or mud. Surviving species live in deep water. Fossils can be found in life position, with the valves closed. Typical length Pholadomya 4cm (11\/2in) ambigua (J. Sowerby); Middle Lias; Early Jurassic; UK. Range: Late Triassic\u2013Recent Distribution: Worldwide Occurrence: Informal name: Clam Group: CARDIIDIA Subgroup: SANGUNIOLITIDAE strongly ridged area Wilkingia muscle scar The thin shell has an iridescent interior. The beaks are placed close to the front of the shell, which has a long, rounded posterior end. The valves have strong, concentric undulations, usually stronger in the middle. The ends of the valves, which are almost smooth in some species, show radial rows of very fine pustules. The hinge line is without teeth, but has a short ridge to hold the ligament. HABITAT It burrowed in the soft sediments of shallow seas. Typical length Wilkingia regularis (King in 3cm (11\/4in) de Verneuil); Great Limestone; Early Carboniferous; UK. Range: Early Carboniferous\u2013Permian Distribution: Worldwide Occurrence:","114 | Invertebrates SCAPHOPODS AND CHITONS THE SCAPHOPOD SHELL is a tapering grows. Chitons have a powerful foot tube, open at both ends, with concentric for gripping hard surfaces, covered ornament or longitudinal ribs. The larger by a shell of eight overlapping valves end contains the animal\u2019s head and held in place by a scaly or spiny girdle. foot, and is buried in the sediment; The valves contain secretory and sense the smaller end is often notched and organs, which reach the surface as is regularly discarded as the animal small pores. Group: DENTALIIDA Subgroup: DENTALIIDAE Informal name: Tusk shell strong, regular ribs Dentalium tube widens at the The narrow, tusk-like, tubular anterior end shell has strong, sharply angular, raised ribs running along its Dentalium sexangulum length. At the smaller, posterior Gmelin in Linnaeus; end the curvature is strong, but this Pliocene; Italy. tends to straighten with growth. The foot and tentacled head emerge from Occurrence: the larger, anterior end of the shell. HABITAT Dentalium lives on the sea floor at a range of depths and temperatures. Typical length 5cm (2in) Range: Middle Triassic\u2013Recent Distribution: Worldwide Group: NEOLORICATA Subgroup: LEPIDOPLEURIDAE Informal name: Chiton Helminthochiton strongly Valves ridged The large shell is made up of a narrow line of median eight squarish valves, ornamented with granules valve and ridges. On the tail valve and median valves are two small flanges, embedded in the girdle tail valve in life and overlapping one another. The head valve is smaller, semicircular, and without flange the flanges. The whole shell is angled ornament of along the back, forming a blunt ridge ridges from head to tail. HABITAT Helminthochiton lived in warm seas on algae-covered debris. Helminthochiton turnacianus Typical length (de Ryckholt); Early 7cm (23\/4in) Carboniferous; Belgium. Range: Early Ordovician\u2013Carboniferous Distribution: Europe, N. America Occurrence:","Invertebrates | 115 GASTROPODS GASTROPODS ARE the largest, most the shell altogether. Shells are composed successful class of molluscs, and have of calcium carbonate, usually in the been able to exploit a wide variety of form of aragonite, but sometimes in marine, freshwater, and land habitats. layers of calcite. An inner nacreous layer They have a head with eyes and a mouth, is characteristic of some more early forms, a flattened foot for crawling, and viscera but the organic outer coat of many living that are generally coiled and carried in a gastropods is usually lost in fossils. Some spiral shell. A few groups cease the coiling families have an inhalant siphon, emerging at some stage, and some have abandoned through a channel in the aperture. Group: VETIGASTROPODA Subgroup: BELLEROPHONTIDAE Informal name: Sea snail Bellerophon trumpet-like, notched aperture The shell is coiled in a single plane, widening rapidly and flared at the aperture. A deep notch in the lip forms a ridge around the mid-line. HABITAT This marine snail probably fed on vegetable matter. Typical length Bellerophon sp.; Top view ribbed or 7.5cm (3in) Carboniferous tubercular Limestone; rows Carboniferous; notches Belgium. forming central ridged band Range: Silurian\u2013Early Triassic Distribution: Worldwide Occurrence: Group: VETIGASTROPODA Subgroup: EUOMPHALIDAE Informal name: Sea snail Euomphalus Euomphalus pentangulus (J. Sowerby); Carboniferous The disc-shaped, coiled shell has Limestone; Carboniferous; a slightly raised spire. The whorls Ireland. are stepped, owing to a narrow notch in the growth lines, forming a sharp ridge. Successive internal walls seal off early whorls. HABITAT It lived on marine vegetation. Typical length 6cm (21\/2in) Top view sharp ridge Range: Silurian\u2013Middle Permian Cross section Distribution: Worldwide Occurrence:","116 | Invertebrates Group: VETIGASTROPODA Subgroup: PLEUROTOMARIIDAE Informal name: Slit shell Pleurotomaria conical spire whorls with rounded Broadly conical, the shell has convex whorls shoulders separated by well-marked sutures. The outer layer is calcitic; the interior is nacreous. In the upper part of the lip is a deep, narrow notch. As the shell grew, the successive positions of this notch formed a groove (selenizone) around the shell, which in life served as an exhalant channel. The shell is ornamented with fine, spiral threads crossed by oblique lines, often thickened to form riblets on the shoulder of the whorl. HABITAT This genus lived in deep waters worldwide. Typical length Pleurotomaria deshayesii groove formed fine, spiral 6cm (21\u20442in) Deslongchamps; Middle by lip notch threads Lias; Early Jurassic; France. Occurrence: Range: Early Jurassic\u2013Early Cretaceous Distribution: Worldwide Group: VETIGASTROPODA Subgroup: FISSURELLIDAE Informal name: Keyhole limpet Diodora exhalant opening Shell exterior The low, conical shell has an oval margin. On the anterior side of the apex is a keyhole-shaped opening used by the animal as an exhalant channel. The shell is ornamented by radiating ribs, alternately thick and thin, crossed by growth lines. HABITAT Diodora lives in shallow water, feeding on sponges and vegetable detritus. narrower Diodora floridana anterior end Gardner; Pliocene; USA. Typical length 5cm (2in) Distribution: Worldwide alternating thick Range: Late Cretaceous-Recent and thin ribs Occurrence:","Group: VETIGASTROPODA Subgroup: SYMMETROCAPULIDAE Invertebrates | 117 Informal name: Cap shell Symmetrocapulus beak coiled apex, now eroded This limpet had a large, cap-shaped shell with an oval margin, ornamented with numerous narrow, radiating ribs interrupted by irregular, concentric folds. The first two small whorls are smooth, turned forward, and dextrally coiled, a little to the left of the shell\u2019s highest point. HABITAT This marine limpet was adapted for grazing on rock surfaces. Symmetrocapulus rugosus narrow ribs short (J. de C. Sowerby); Inferior anterior Oolite; Middle Jurassic; France. slope Typical length Distribution: Europe, N. America Occurrence: 3.5cm (11\u20444in) Range: Jurassic\u2013Eocene Group: VETIGASTROPODA Subgroup: PLATYCERATIDAE Informal name: Sea snail Platyceras regularly coiled Platyceras haliotis apical whorls (J. de C. Sowerby); The first few whorls of the shell Wenlock Limestone; are loosely coiled but rapidly Silurian; UK. enlarging, so that the last whorl is inflated and margin follows more or less cap-shaped. shape of substrate Sinuous growth lines produce prominent ridges and furrows which indent the shell margin. These had no functional significance but followed the shape of the object on which the animal lived \u2013 and so they vary between individuals. HABITAT Commensal with Typical length inflated body crinoids, Platyceras shells are 2cm (3\u20444in) whorl, with occasionally preserved in ridges their life position on the host. Range: Silurian\u2013Early Carboniferous Distribution: Worldwide Occurrence:","118 | Invertebrates Group: VETIGASTROPODA Subgroup: TROCHIDAE Informal name: Top shell Calliostoma shallows sutures Shaped like a regular cone with flattened sides, the thinnish shell has shallow sutures separating the whorls. The whorls flat-sided whorls are ornamented with a number of fine, spiral cords, often with granular, bearing numerous round granules. These cords are spiral cords continued on the flat base, which has no umbilicus. The oblique lip partly conceals the aperture. oblique lip HABITAT Various species Calliostoma inhabit rocky shores. nodulosum (Solander Occurrence: in Brander); Barton Clay Formation; Middle Eocene; UK. Typical length iridescent interior 3cm (11\u20444in) Range: Early Cretaceous\u2013Recent Distribution: Worldwide Group: VETIGASTROPODA Subgroup: NERITIDAE Informal name: Nerite Velates partly obscured spiral apex This nerite had a thick, heavy, oval shell with a low, conical spire. The early whorls are regularly coiled and visible at the apex, in the right posterior quarter of the shell. A layer of polished enamel over the spire obscures the spiral coiling and forms a thick pad over the base, ending in a toothed shelf halfway across the aperture. A separate shelly place (operculum) closed the aperture in life. HABITAT Velates lived on sand in shallow waters \u2013 its shell\u2019s weight providing stability in strong currents. thickened smooth, folded layer pad of polished enamel Range: Early\u2013Middle Eocene narrow, semi- Velates perversus circular aperture (Gmelin); Early Eocene; France. shelf with row of denticles outer lip Typical length Distribution: Worldwide 3cm (11\u20444in) Occurrence:","Group: CAENOGASTROPODA Subgroup: VIVIPARIDAE Invertebrates | 119 Viviparus Informal name: Pond snail Viviparus angulosus The small- to medium-sized, thin, brittle shell has evenly (J. Sowerby); Headon rounded whorls, which are generally convex and Hill Formation; Late smooth, and crossed by faint growth lines. The lip is Eocene; UK. vertical in profile and the aperture oval with a continuous margin, slightly narrowed at the rounded top. This margin almost hides the narrow whorls umbilicus. In life, the aperture is closed by a flexible, horny plate. edge of aperture HABITAT Viviparus lives in freshwater lakes, Occurrence: swamps, and slow rivers. Informal name: Sea snail REMARK Because they can tolerate only the slightest degree of salinity, shells of Viviparus are regularly an excellent indicator of non-marine conditions increasing in the fossil record. whorls Typical length umbilicus moderately 2.5cm (1in) partly concealed long spire with clearly indented by inner lip suture Range: Middle Jurassic\u2013Recent Distribution: Worldwide narrow, flat, spiral ribbons Group: CAENOGASTROPODA Subgroup: COELOSTYLINIDAE Bourguetia The large and moderately thick shell of Bourguetia has convex whorls separated by well-marked sutures. Its extended spire appears slightly turreted and is a little longer than the final whorl. The upper part of the shell is ornamented with shallow grooves, dividing the surface into narrow, flat, spiral ribbons. On the basal part of the shell these become thicker, more prominent cords. The aperture is oval with a continuous margin. HABITAT Despite a superficial similarity to Viviparus (see above), Bourguetia was a fully marine snail that lived among coral and sponge reefs in warm and shallow seas. Bourguetia more prominent Typical length saemanni (Oppel); cords on base 11cm (41\u20442in) Osmington Oolite; Middle Jurassic; UK. Distribution: Europe, New Zealand Occurrence: Range: Middle Triassic-Late Jurassic","120 | Invertebrates Subgroup: THIARIDAE Informal name: Marsh creeper Group: CAENOGASTROPODA Brotia shelly plug in apex Brotia has a narrow, elongate, and turreted shell. When no longer in use, juvenile whorls are sealed off with a plug and then discarded sharp, oblique or eroded away. The variable ornament usually consists of a few ribs sharp, spiral cords broken up by the low, oblique ribs. The denticulate uppermost cord has the most prominent denticles and shoulder cord sets off the smooth concave shoulder. There is a broad, V-shaped embayment high on the V-shaped growth lines showing lip and a weak channel at the base of former positions of lip the aperture. HABITAT Brotia feeds on detritus in the mud of warm, brackish lagoons. Brotia melanoides (J. de C. Sowerby); Woolwich Beds; Paleocene; UK. broad, shallow Distribution: Europe, Asia Typical length 4cm (11\/2in) channel Occurrence: Range: Paleocene\u2013Recent Group: CAENOGASTROPODA Subgroup: TURRITELLIDAE Informal name: Screw turret plugged apex Turritella Turritella terebralis The shell of Turritella is a narrow, elongate cone with flattened Lamarck; Coquillat sides. Whorls increase in size slowly, each one slightly overhanging de Leognan the next. The tip of the spire is often sealed off and discarded, as Formation; Early in Brotia. The few distinct spiral cords on the early whorls Miocene; France increase in number as the shell grows. The aperture is nearly round, with a thin lip, often showing signs of breakages. HABITAT Turritella is a suspension feeder, usually abundant in shallow off- shore waters. Range: Late Eocene\u2013Recent thin lip Typical length 6cm (21\/2in) Occurrence: round aperture with no channel at base Distribution: Worldwide","Invertebrates | 121 Group: CAENOGASTROPODA Subgroup: CAMPANILIDAE Informal name: Giant cerith Campanile Shell cut in half A giant among gastropods, the shell of Campanile can reach a length secondary of 60cm (24in), and if this could be uncoiled, it would make a tube over thickening 3m (I0ft) long. There may be more than 30 whorls constructed in the rectangular whorls animal\u2019s lifetime, but the earlier ones are back-filled with shell once they have been evacuated, and are periodically lost by abrasion, leaving tip worn flat the apex sealed. Early whorls are turreted by an upper row of Campanile giganteum tubercles, with finer cords below. (Lamarck); Calcaire On the last few whorls the ornament Grossier; Middle deteriorates, leaving a single row Eocene; France. of blunt knobs. The large, flared aperture is developed only on two oblique fully adult shells. The central ridges on pillar (columella) is strengthened columella by two encircling ridges which are obsolete at the aperture but can be seen clearly when distinct cords the shell is broken. A calcified on spire whorls outer layer is covered with rows of small pits. HABITAT Campanile feeds on prominent row algae on sandy bottoms in very of knobs shallow, warm seas. The tip of the heavy shell trails behind it as it crawls, eventually wearing flat on one side. REMARK Only a single species survives today, in the shallow coastal waters off Australia. fine, curved growth lines pitted outer weakening ridges immature layer on columella outer lip Typical length 30cm (12in) Range: Late Cretaceous\u2013Recent siphonal channel Distribution: Worldwide Occurrence:","122 | Invertebrates Group: CAENOGASTROPODA Subgroup: APORRHAIDAE Informal name: Pelican\u2019s foot spine joined to spire Tessarolax curved basal The small, biconical, ridged shell of Tessarolax was spine much enlarged by having the extremities drawn out into four slender and delicate, curved spines. The bases of these are connected by an outgrowth of the lip, like the web of a duck\u2019s foot. HABITAT This creature was probably a detritus feeder, living on muddy sand in moderately deep water. REMARKS The spines may have helped to prevent the shell sinking into the substrate. Tessarolax fittoni (Forbes); Lower Greensand; Early Cretaceous; UK. Typical length 6cm (21\/2in) lip enlarged with two labial spines Range: Cretaceous Distribution: Worldwide Occurrence: Group: CAENOGASTROPODA Subgroup: STRUTHIOLARIIDAE Informal name: Ostrich foot Struthiolaria stepped spire whorls with deep sutures This sturdy, medium-sized mollusc has a proportionately large body whorl and a turreted growth lines spire. Distinct sinuous lines mark the positions following lip profile of the lip during growth. When adult, both the lip and the inner margins of the aperture are thickened with enamel, which spreads to form a pad. Spiral cords often ornament the whole shell, with a series of ribs or nodes on the whorl shoulder. Some species, however, are smooth and polished. HABITAT This genus feeds on algal detritus in shallow waters. aperture Struthiolaria ameghinoi enamelled (von Ihering); Santa Cruz and thickened Formation; Early Miocene; into a pad Argentina. Typical length 4cm (11\/2in) Distribution: Australasia, S. America Occurrence: Range: Paleocene\u2013Recent","Invertebrates | 123 Group: CAENOGASTROPODA Subgroup: STROMBIDAE Informal name: Beak shell Rimella Rimella fissurella (Linnaeus); Calcaire The elongate shell of Rimella had gently convex whorls, Grossier; Middle Eocene; France. ornamented with numerous sharp ribs. The spiral tip of channel sculpture consists of close cords, largely obsolete bent near apex in some species. The aperture is narrow and lens-shaped, and the last whorl convex tapers down to a narrow rostrum, whorls separated from the lip by a distinct notch. When adult, a long, narrow channel was secreted from the upper corner of the aperture to the apical area, where it was usually bent round. As this channel was too narrow to accommodate the syphon, its function is unclear. HABITAT Rimella was notch in probably a herbivorous snail base of lip that lived in the muds and sands of warm, shallow seas. Typical length inner channel connects 2.5cm (1in) with aperture Range: Paleocene\u2013Oligocene reflected lip Distribution: Worldwide Occurrence: Group: CAENOGASTROPODA Subgroup: HIPPONICIDAE Informal name: Sorting hat shell Hipponix tiny coiled apex, now eroded The small- to medium-sized, cap-like shell tends to be rather variable in shape. The fine, radiating margin shaped juvenile shell is smooth and coiled threads to contours of slightly to the right of the apex, but substrate is soon worn away leaving a blunt point. The adult shell expands Hipponix dilatatus (Lamarck); rapidly to form a low cone Calcaire Grossier; Middle with an extended beak which Eocene; France. often overhangs the rear shell margin. It is ornamented with close, fine, radiating ridges. HABITAT Hipponix lives on other shells and corals in warm, shallow seas, feeding on particles in suspension. Range: Late Cretaceous\u2013Recent Distribution: Worldwide Typical length 4cm (11\/2in) Occurrence:","124 | Invertebrates Group: CAENOGASTROPODA Subgroup: CALYPTRAEIDAE Informal name: Slipper limpet Crepidula growth line showing Crepidula falconeri earlier margin Newton; Middle Beginning with one simple juvenile Eocene; Nigeria. whorl, Crepidula rapidly expands into simple, one-turn, an elongate-oval body whorl, smooth spiral apex irregularly wavy margin in some species but ridged or spiny in matches substrate others. On the underside, the wide aperture is half covered by a thin, Occurrence: polished shelf (septum), which protects the viscera. HABITAT The animal is a filter feeder in shallow seas. Its sedentary habit is indicated by the irregular, wavy shell margin, which conforms to the shape of the substrate. Typical length 2cm (3\u20444in) Range: Late Cretaceous\u2013Recent Distribution: Worldwide Group: CAENOGASTROPODA Subgroup: XENOPHORIDAE Informal name: Carrier shell Xenophora This has a moderately low, conical shell with shallow sutures, ornamented with oblique, interrupted ridges. The flat base with its narrow aperture is overhung by a thin, wavy peripheral margin. HABITAT Hidden beneath its shell, the animal browses on micro-organisms in the silty mud of fairly deep waters. REMARK Xenophora has acquired the habit of selecting bits of shell or other debris from the sea bed and cementing them to the lobes of the periphery, where they become incorporated. smaller debris attached when younger periphery of Basal view earlier whorl constricted aperture with concave lip Xenophora crispa (K\u00f6nig); Pliocene; Italy. objects cemented to the Side view peripheral lobes Typical length margin support the shell 3cm (11\u20444in) Distribution: Worldwide Range: Late Cretaceous\u2013Recent Occurrence:","Invertebrates | 125 Group: CAENOGASTROPODA Subgroup: CYPRAEIDAE Informal name: Egg cowrie Umbilia outer lip curled inwards This cowrie has a large, globular shell with a apical spout, flattened underside, narrowed at each end. The bent sideways spire is a flat coil obscured by a shiny enamel coating, which covers the rest of the shell. flat spire, When adult, the lip is inflated and partly wholly curled inwards, narrowing covered the long aperture. This curves towards the top and is guarded by a line of strong, ridge-like teeth on the body whorl, and by a row of finer denticles on the lip. HABITAT Most cowries feed on detritus but the habits of Umbilia are not well known. aperture small tubercles globular body lips lined with whorl, glazed with different-sized layer of enamel teeth Typical length Umbilia eximia (G.B. Sowerby); 3.5cm (11\u20444in) Miocene; Australia. Range: Middle Oligocene\u2013Recent Distribution: Australia Occurrence: Group: CAENOGASTROPODA Subgroup: NATlCIDAE Informal name: Moon shell Natica Natica shell, Prey shell apical view The smooth, globular shell has a large body feeding whorl with a much smaller spire, and an hole drilled umbilicus with a central ridge. The outer in bivalve lip is thin, and the aperture is closed in life by a right-fitting operculum. Natica stercusmuscarium HABITAT This gastropod lives at various (Gmelin); Pliocene; Italy. depths in marine to slightly brackish Occurrence: waters. It is carnivorous, drilling bevel-edged holes in other mollusc shells and sucking out the contents. Typical length 3cm (11\u20444in) Range: Paleocene\u2013Recent Distribution: Worldwide","126 | Invertebrates Subgroup: CASSIDAE Informal name: Helmet shell flat-sided Group: CAENOGASTROPODA spire Phalium reflected lip row of shoulder Phalium has a strong, medium-to-large shell, with nodes an inflated body whorl ornamented with both tubular siphonal spiral and transverse threads, and two to four spiral channel rows of tubercles. The uppermost of these is Occurrence: situated on the angulated shoulder of the whorl, giving rise to a low, flat-sided, conical spire. The reflected and thickened lip is corrugated inside, and a roughly ridged layer of enamel is spread around the aperture on to the body whorl. At the bottom of the aperture, and bent away from it, is the tubular siphonal channel. HABITAT Phalium is an active predator, living on coral rubble or sand in warm waters. Typical length Phalium decussatum 10cm (4in) (Linnaeus); Calcaire Grossier; Middle Range: Paleocene\u2013Recent Eocene; France. Distribution: Worldwide Group: CAENOGASTROPODA Subgroup: FICIDAE Informal name: Fig shell Ficopsis narrow apex Ficopsis had a thinnish shell tapering to distinct a narrow rostrum. The raised spire, which spire is much shorter than the body whorl, has gently convex whorls, a narrow apex, slight and well-defined sutures. A latticework shoulder of fine, regular threads covers the angle whole shell. The body whorl is network of fine, convex and varies from being raised threads evenly rounded to having a polygonal profile, caused by narrow rostrum the accentuation of the slight shoulder and spiral ridges. long, nearly The aperture is thin-lipped straight siphonal and ovate, narrowing into a long siphonal channel. channel HABITAT This animal lived on sandy substrates in warm regions. Typical length Ficopsis penita 6cm (21\/2in) (Conrad); Gosport Sands; Middle Eocene; USA. Range: Eocene Distribution: N. America, Europe Occurrence:","Group: CAENOGASTROPODA Subgroup: EPITONIIDAE Invertebrates | 127 Informal name: Wentletrap Cirsotrema deep sutures Cirsotrema has an elongate calcitic shell, with convex ribs made up whorls separated by deep sutures, and an ornament of laminae of numerous raised and frilled ribs, each made up of a number of compressed laminae. In some less prominent species they connect up from one whorl to spiral ornament the next. The last rib frames the small, basal cord circular aperture. A few weak spirals are visible between, circular aperture and sometimes cross, the ribs, with no siphonal while the base of the shell is channel surrounded by a strong cord. Typical length HABITAT This marine- 3cm (11\/4in) dwelling animal is carnivorous, using its long proboscis to feed on sedentary creatures. Cirsotrema lamellosum (Brocchi); Pliocene; Italy. Range: Paleocene\u2013Recent Distribution: Worldwide Occurrence: Group: CAENOGASTROPODA Subgroup: MURICIDAE Informal name: Comb shell Murexsul turreted spire with deep sutures Murexsul has a medium-sized shell with sharp ribs and a long rostrum. The whorls are sharply shouldered and the sutures deep, giving rise to a turreted spire ornamented with closely packed spiral cords. These rise at intervals to form a rib, composed of a wall of fluted spines. The last rib surrounds the smooth, enamelled aperture, slightly detached from the rest of the shell. The base of the aperture is suddenly narrowed into a siphonal channel, which is virtually closed to form a tube, and this rostrum is armed with a few more spines. HABITAT Murexsul is a carnivore, inhabiting moderately deep waters. Typical length Murexsul thick, rounded, 9cm (31\/2in) octogonus spiral ridges (Quoy & Gaimard); rib made of row Late Pliocene; of tubular spines New Zealand. spiny rostrum Range: Miocene\u2013Recent Distribution: Australasia, W. Pacific Occurrence:","128 | Invertebrates Group: CAENOGASTROPODA Subgroup: MURICIDAE Informal name: Sea snail Ecphora turreted spire simple sculpture Ecphora is one of the best known and most striking fossil gastropods. The spire of its shell is relatively of strong keels small and turreted, and the whorls are dominated by two prominent encircling keels which suture are often grooved along their length. One or two more keels appear on the base tubular ends of the body whorl. The siphonal of former channel is sharply bent back channels from the aperture, and a chain of the spouts of previous Ecphora quadricostata channels makes a spiral (Say); Yorktown around the rostrum. Formation; Pliocene; USA. HABITAT This creature was a carnivorous predator, living in shallow waters. basal wall extension Typical length 10cm (4in) Range: Late Oligocene\u2013Pliocene Distribution: N. America, Europe Occurrence: Group: CAENOGASTROPODA Subgroup: NEPTUNEIDAE Informal name: Whelk stepped spire Neptunea ornament of The shell of this large whelk has rounded whorls fine, spiral separated by deep sutures. Some species coil threads dextrally, as most gastropods do, but others are growth stages typically sinistral. A fairly long and stepped spire leads in to a convex body whorl. The large, ovate aperture has a rather short and broad siphonal channel. If present, ornament is restricted to spiral lines, cords, or keels, although coarse, transverse growth lines may occur. HABITAT A cold-water carnivore, Neptunea preys on bivalves and other invertebrates in moderately to very deep seas. sinistral coiling Neptunea angulata Distribution: Worldwide Typical length 9cm (31\u20442in) Harmer; Red Crag; Occurrence: Late Pliocene; UK. Range: Late Eocene\u2013Recent","Invertebrates | 129 Group: CAENOGASTROPODA Subgroup: FASCIOLARIIDAE Informal name: Sea snail Clavilithes early sculpture Cross- section Clavilithes had a medium to large, fusiform stepped spire shell. The young shell begins as a smooth with smoother ovate column of equal-sized whorls, developing whorls aperture low ribs crossed by spiral threads. The with sculpture soon dies away, leaving only a shelf siphonal few spiral lines, and the whorls become canal flat-sided. A sharp shelf at the top of the whorl gives the spire a stepped shape. The last whorl is usually cup-shaped and the aperture oval. HABITAT Probably carnivorous, this Clavilithes pinus body whorl gastropod was an inhabitant of sand, silt, (Perry); Barton narrows and mud in moderately deep, warm waters. Clay Formation; abruptly Middle Eocene; Typical length 12cm (43\u20444in) UK. Range: Paleocene\u2013Pliocene Distribution: Worldwide Occurrence: Group: CAENOGASTROPODA Subgroup: VOLUTIDAE Informal name: Volute Volutospina The medium to large, biconic shell has an acutely pointed apex. Despite the shallow sutures the spire has a turreted appearance, caused by the short ribs which end in sharp spines on the shoulder. The body whorl is ornamented with weak, flat, spiral ribbons, crossed by numerous inconspicuous vertical growth lines. The rather narrow aperture tapers down to an open siphonal channel and the outer lip is not thickened. There are several ridges on the columella, the lowest one being the strongest, and a layer of enamel spreads from the interior on to the body whorl. Volutospina luctator (Solander in Brander); HABITAT This creature inhabited sandy Barton Clay Formation; or muddy sea beds in warm waters. Middle Eocene; UK. REMARK Like other volutes, Volutospina was a fast- moving predator. narrow apex low ribs with prominent rostrum with siphonal channel Typical length 7cm (23\u20444in) spines Occurrence: Range: Late Cretaceous\u2013Pliocene Distribution: Worldwide","130 | Invertebrates Group: CHAENOGASTROPODA Subgroup: PSEUDOLIVIDAE Informal name: False olive low spire Pseudoliva build-up of The medium-sized, near-spherical shell enamel below of Pseudoliva has a depressed spire with a suture small, central, projecting apex. The ovate body whorl has a humped shoulder owing apex to enamel being secreted below the suture. Species are variably ornamented with nodes, ribs, or coarse growth lines. The aperture is wide, with a broad siphonal channel. Low down on the thin outer lip is a deep and narrow depression, which gives rise to a sharp groove around the shell. HABITAT Pseudoliva wide and shallow groove ends lives on sand and silt in siphonal channel in lip notch shallow waters. REMARK One species survives in west Africa. Pseudoliva laudunensis sharply incised Typical length (Defrance); London Clay; groove around 3cm (11\/4in) Early Eocene; UK. base of whorl Distribution: Worldwide Occurrence: Range: Late Cretaceous\u2013Recent Group: CHAENOGASTROPODA Subgroup: CONIDAE Informal name: Cone shell Eoconus low, tightly coiled spire Eoconus has a strong, medium-sized shell with a largely smooth, conical body whorl, strongly platform angled to form a narrow platform at the top. at top of The spire is stepped and depressed with a whorl prominent central apex. A thin lip, parallel thin outer lip with the body, forms the straight, narrow aperture running the length of the whorl. Typical length 6cm (21\/2in) HABITAT These creatures live in warm waters on sand, silt, or hard bottoms, at Occurrence: a variety of depths. REMARK The Conidae are predatory; they hunt worms, molluscs, and even fish, using teeth that are adapted to function as effective poison darts. Eoconus sauridens narrow channel Conrad; Stone City Form- and aperture ation; Middle Eocene; USA. Range: Late Cretaceous\u2013Recent Distribution: Worldwide","Group: CHAENOGASTROPODA Subgroup: CLAVATULIDAE Invertebrates | 131 Informal name: Turrid Eosurcula long spire This turrid had an elongate, spindle-shaped shell with loosely strong, spiral coiled whorls. The spire is long and slender with shallow but threads below distinct sutures, and the whorl profile is weakly angled shoulder below the shoulder. The lens-shaped aperture gradually sinus band tapers into the siphonal channel, housed in a long, on shoulder fine rostrum. Just below the top of the thin, curved lip is a characteristically deep, Typical length rounded sinus. The shell is ornamented 3cm (11\/4in) with strong spiral threads, crossed by close, fine growth lines. HABITAT Like other turrids, anal sinus in lip Eosurcula was a predator, living on sand in moderately deep waters. siphonal channel in Eosurcula moorei (Gabb); long rostrum Stone City Formation; Middle Eocene; USA. Range: Eocene Distribution: N. America Occurrence: Group: HETEROBRANCHIA Subgroup: ARCHITECTONICIDAE Informal name: Sundial shell Granosolarium Basal view Granosolarium has a low, conical shell on which the tiny initial whorls are smooth and slightly inturned, and marked off by a collar. Beneath the sharply angled periphery the base is almost flat. In the centre, the wide, funnel-shaped umbilicus exposes the lower side of the whorls all the way to the apex. The whole shell is ornamented with granulated, spiral cords crossed by oblique growth lines. HABITAT This mollusc lives in shallow to moderately deep waters, probably as a parasite of corals or other sedentary animals. triangular sharply angled aperture periphery ornament of granulated base with wide spiral cords umbilicus Granosolarium Top view Typical length elaboratum 4cm (11\/2in) (Conrad); Gosport Sands; Distribution: Worldwide Middle Eocene; USA. Occurrence: Range: Late Cretaceous\u2013Recent","132 | Invertebrates Subgroup: BULLIDAE Informal name: Bubble shell Group: CEPHALASPIDEA Bulla apical umbilicus Bulla has a rather thin, almost spherical shell, only one top of whorl of which is visible. The few tiny initial whorls coil aperture sinistrally, but the shell then resumes dextral coiling. reaches Each whorl wholly encloses the previous one, so that apex there is no apparent spire. The aperture is at least as long as the shell, and an enamel layer near-spherical strengthens the columella wall. body whorl HABITAT Unlike some of its nearest relatives, this is a herbivorous animal living on sandy or muddy bottoms in shallow, warm waters. REMARK An unusual feature of this gastropod is that its body is twice the size of the shell and is unable to withdraw into it. Bulla ampulla enamel on Typical length Linnaeus; Reef limestone; columella wall 2cm (3\/4in) Pleistocene; Red Sea. Range: Late Jurassic\u2013Recent Distribution: Worldwide Occurrence: Group: HETEROBRANCHIA Subgroup: NERINEIDAE Informal name: Auger shell concave whorls Nerinea between spiral keels Nerinea had a long, narrow shell, typically with concave columella sides to the whorls and accentuated keels just over the ridges sutures. The apex, only rarely preserved, is a tiny flat coil which stands at right-angles to the axis of the main shell. A characteristic of the genus is a collection of fine ridges and processes on the walls of the small aperture; there may be up to seven of these, best seen in cross-sections. HABITAT Nerinea is often associated with coral reef deposits. Nerinea sp.; Cretaceous; Israel. columella ridge visible in aperture internal ridge Typical length Distribution: Worldwide Young shell in 6cm (21\/2 in) cross-section Range: Early Jurassic\u2013Late Cretaceous Occurrence:","Group: BASOMMATOPHORA Subgroup: PLANORBIDAE Invertebrates | 133 Informal name: Ramshorn snail Australorbis flat base with faint ornament Rather thin and disc-shaped, the shells of this family are in fact sinistrally coiled, although they appear to be dextral. The inverted spire takes the form of a deep and widely open umbilicus containing close, convex whorls. Bluntly angled at the periphery, the base is flat and ornamented with occasional weak, spiral lines. Oblique growth lines cover the whole shell. The aperture is small and triangular\/oval. HABITAT Today, the family, Planorbidae, is Basal view known to live exclusively in fresh water, and the genus Australorbis feeds on vegetable sinistral shell that matter in lakes, marshes, and rivers. appears to be It is fairly certain that this was built upside down always the case, so this fossil is a useful indicator of non-marine conditions in the past. small, oval Top view aperture deeply sunk Typical length Australorbis whorls 3cm (11\/4in) euomphalus (J. Sowerby); Headon Hill Formation; Late Eocene; UK. Range: Late Cretaceous\u2013Recent Distribution: Europe, Asia, N. & S. America Occurrence: Group: STYLOMMATOPHORA Subgroup: CLAUSILIIDAE Informal name: Land snail Rillyarex shallow sutures The large shell is sinistrally coiled, unlike most gastropods. The elongate spire is narrowly arched in profile, with gently rounded sides, hardly indented by the shallow sutures and slightly convex whorls. The whole shell is ornamented with numerous oblique, transverse ridges. The ovate aperture has a continuous, slightly flared rim, except at its upper junction. HABITAT Although larger than its ridged living relatives, Rillyarex had all the ornament characteristics of an air-breathing terrestrial snail and was probably aperture with rim Typical length washed into the freshwater 7cm (23\/4 in) deposits in which it is found. Rillyarex preecei Nordsieck; Bembridge Limestone; Late Eocene; UK. Range: Middle Eocene\u2013Oligocene Distribution: Europe Occurrence:","134 | Invertebrates NAUTILOIDS NAUTILOIDS ARE EARLY, marine into a body chamber and many cephalopods that possess a shell. smaller chambers. The chambered They were most abundant in the part of the shell is known as the Palaeozoic Era \u2013 400 million years ago; phragmocone. Nautiloids have heads today, only a single genus survives \u2013 with well-developed eyes, and grasping the pearly nautilus of the south-west tentacles. They swim by squirting water Pacific Ocean. The shell is divided out of the body cavity. Group: ORTHOCERIDA Subgroup: ORTHOCERATIDAE Informal name: Orthoceras Orthoceras separate chambers of phragmocone The shell of Orthoceras is shaped like a slowly tapering cylindrical cone, and is made up of closely spaced concavo-convex chambers, joined together by a centrally placed tube called the siphuncle. HABITAT Orthoceras was an active swimmer, Internal mould with the shell positioned horizontally of phragmocone in the water. It scavenged and predated on small animals. Orthoceras sp.; MacDonnell Ranges; Middle convex posterior Ordovician; Australia. of chamber Typical length 15cm (6in) Range: Middle Ordovician Distribution: Worldwide Occurrence: Group: ORTHOCERIDA Subgroup: CYRTOCERATIDAE Informal name: Nautiloid Cyrtoceras numerous short long living chamber chambers The shell is strongly curved in an open hook Typical length shape, and nearly circular in cross-section. Cyrtoceras sp.; 12cm (43\/4in) The posterior part is made up of numerous Ordovician; closely spaced chambers, while the long Czech Republic. living chamber makes up the anterior part of the shell. blunt termination HABITAT Experiments suggest that the animal lived head-down in the water, probably near the bottom of the sea. It was able to swim and alter its buoyancy. REMARKS The specimen featured is an internal mould, from which the original shell has been completely lost. Range: Ordovician Distribution: Worldwide Occurrence:","Group: ACTINOCERATIDA Subgroup: HURONIIDAE Invertebrates | 135 Huronia limestone Informal name: Nautiloid matrix Shells of this genus have a large, straight siphuncle, large segments with long segments separated by strong constrictions. of siphuncle Complex canals are present. The central canal Typical length 20cm (8in) is very narrow. Occurrence: HABITAT This genus lived in shallow seas as a scavenger or predator. It was able to swim and adjust its position in the water column by moving liquid along the siphuncle from chamber to chamber. REMARK Only the robust siphuncle of this species is preserved in the specimen. The chambers and outer wall are missing. Huronia vertebralis strong Stokes; Ordovician; Canada. constrictions Range: Ordovician\u2013Silurian Distribution: N. America Group: ORTHOCERIDA Subgroup: ORTHOCERATIDAE Informal name: Orthoceras Orthoceras limestone phragmocone siphuncle The late Silurian and early Devonian Orthoceras Limestones of the Erfoud area in south-eastern Morocco are well calcite-filled known for their spectacularly preserved orthocone chambers cephalopods and goniatites. The stone is extensively quarried and turned into a variety of items including siphuncle crockery, paperweights, bathroom sinks, and huge wall plaques, which are sold worldwide. The Paperweights\/ orthocone assemblage comprises scores of Letter openers different species, however one of the most abundant is Orthocycloceras fluminense. HABITAT Orthoceras limestone was deposited in a shallow, highly productive shelf sea, probably under slightly anoxic (low oxygen) conditions judging by the lack of bottom- dwelling organisms. REMARK The genus Orthoceras itself is restricted to a single Ordovician species. Typical length 30cm (12in) Orthocycloceras fluminense (Meneghini); Late Silurian; Morocco. Range: Silurian\u2013Devonian Distribution: Worldwide Occurrence:","136 | Invertebrates Group: NAUTILIDA Subgroup: TRIGONOCERATIDAE Informal name: Nautiloid Discitoceras mould of fine, spiral another fossil ribs This nautiloid had an evolute shell with rounded a widely open umbilicus and a rounded venter venter. A spiral ornament of fine, closely spaced ribs is present on the shell\u2019s exterior. HABITAT Discitoceras lived around deep-water algal reefs in the Early Carboniferous seas and probably swam poorly, like the living pearly nautilus. REMARK An external mould of another specimen is present on the outside of the living chamber. Typical diameter Discitoceras 15cm (6in) leveilleanum (de Koninck); Carboniferous Limestone; Early Carboniferous; lreland. Range: Early Carboniferous Distribution: N.W. Europe Occurrence: Informal name: Nautiloid Group: PSEUDORTHOCERIDA Subgroup: CARBACTINOCERATIDAE Rayonnoceras The shell of Rayonnoceras is straight and conical, with a smooth surface. The centrally placed siphuncle has a complex structure. Both the siphuncle and the convex chambers are filled with calcareous deposits formed during the life of the nautiloid. HABITAT Rayonnoceras was probably a bottom-dwelling, ambush predator in a shallow-water marine environment. REMARK The calcareous deposits in the shell are thought to have acted as ballast, to make the animal heavier. Rayonnoceras large, complex siphuncle giganteum (J. Sowerby); chambers Typical diameter Carboniferous filled with 20cm (8in) Limestone; Early calcareous Carboniferous; deposits Occurrence: lreland. Distribution: Europe, N. America Range: Early Carboniferous","Group: NAUTILIDA Subgroup: TRIGONOCERATIDAE Invertebrates | 137 Vestinautilus Informal name: Nautiloid The shell is notable for its extremely Vestinautilus evolute form. It has an open umbilicus cariniferous and a distinctive mid-flank ridge, which (J. de C. Sowerby); runs along each side, on which the Carboniferous; sutures form a forwardly directed Locality unknown. V-shaped fold. There are numerous small chambers. open umbilicus HABITAT Vestinautilus was a poor swimmer, living on the bottom of shelf seas. REMARK The specimen is preserved as an internal mould in limestone; the body chamber has broken away. The sutures are well displayed. Range: Early Carboniferous folded suture Typical diameter Distribution: Europe, USA, S. America 6cm (21\/2in) Occurrence: Group: NAUTILIDA Subgroup: NAUTILIDAE Informal name: Nautilus Eutrephoceras Eutrephoceras dekayi (Morton); Pierre Shale The coiling of the shell is very involute, the Formation; Late umbilicus extremely narrow. The outline Cretaceous; USA. of the shell is nearly globular; the venter is very broadly rounded. The individual patches of original chambers of the phragmocone are fewer shell material than in the genus Cenoceras (see p.139). large chambers HABITAT Eutrephoceras probably narrow umbilicus lived as a slow-moving predator in the rather shallow waters of the Western Typical diameter Interior Seaway, which occupied the 10cm (4in) mid-west of the USA during much of the Late Cretaceous period. Occurrence: REMARK This particular specimen is preserved as an internal mould in dark mudstone, on the surface of which patches of the original shell material adhere. These patches of shell have the \u201cmother of pearl\u201d colours that are characteristic of all cephalopod shells. Range: Late Cretaceous Distribution: USA","138 | Invertebrates Subgroup: CENOCERATIDAE Informal name: Nautilus Group: NAUTILIDA Cenoceras Internal mould This is an extinct, long-ranging broad, genus of nautiloid. The rounded planispiral shell varies from venter loosely to tightly coiled and discoidal to globose in shape. The siphuncle is usually situated centrally in each compartment of the phragmocone. The outer surface is generally smooth but may be finely ribbed and ornamented in some species. The living chamber occupies about half a whorl. HABITAT Like the living Nautilus, Cenoceras was likely to have been a marine predator and an opportunistic ocean-floor scavenger. REMARK Nautiloids can change their buoyancy by altering the proportions of gas and liquid in their chambers. This allows them to vertically migrate from deep to shallow water at night. Many Cenoceras shells are broken having imploded, a result of the shell sinking into deeper water after the animal died. Cross-section mud-filled chambers narrow umbilicus simple, curved Cenoceras sp.; sutures Inferior Oolite; Middle Jurassic; UK. broken Cenoceras chamber walls bradfordense (Crick); Inferior Oolite; Middle Jurassic; UK. siphuncle joining start of living Typical diameter chambers chamber 15cm (6in) Range: Late Triassic\u2013Middle Jurassic Distribution: Worldwide Occurrence:","Cross-section Invertebrates | 139 concavo-convex broken chambers chamber wall growth lines body chamber original missing aragonite outer wall shell shell fine radial siphuncle ribs Cenoceras sp.; Cenoceras simillimum Inferior Oolite; (Foord & Crick); Lower Middle Jurassic; UK. Lias; Early Jurassic; UK. Side view narrow umbilicus irregular folds aperture","140 | Invertebrates Group: NAUTILIDA Subgroup: ATURIIDAE Informal name: Nautilus Aturia Internal mould The shell is very involute and compressed, with a narrow, shallow strong fold in umbilicus and a rounded venter. suture line The suture line has a strong, backward-pointing fold narrow on the flank, which umbilicus gives it a superficial resemblance to some rounded primitive Palaeozoic venter ammonoids. Aturia HABITAT Aturia praeziczac probably lived in (Oppenheim); relatively deep water; Eocene; Egypt. the compressed shell was streamlined to Occurrence: allow fast movement. Informal name: Rhyncholite REMARK The specimen is an internal Upper jaw mould of the chambered part of the shell. Typical length Distribution: Worldwide 3cm (11\u20444in) Range: Paleocene\u2013Miocene Group: NAUTILIDA Subgroup: VARIOUS Rhyncholites Rhyncholites is the genus given to the fossilized remains of the upper jaw of a nautiloid. Like the living nautilus, the nautiloids had two strong biting jaws, resembling the beak of a parrot. Composed of calcite, they preserved well. These jaws were ideal for cutting fish and crustacea. Typical length biting edge Rhyncholites 12cm (43\u20444in) Distribution: Worldwide sp.; Eocene; Libya. Range: Triassic\u2013Pliocene Occurrence:","Invertebrates | 141 AMMONOIDS AMMONOIDS EVOLVED from nautiloids the siphuncle (the tube connecting the in the early Devonian period, about chambers of the shell), which is near 400 million years ago, and were abundant the outside of the shell (ventral). in world seas for the following 370 million Ammonoidea sutures can be simple, as years, after which they vanished suddenly found in Palaeozoic species, or complex, at the end of the Cretaceous period. The as seen in Mesozoic species. Because rapid evolution of ammonoids and their they are extinct, we know very little widespread distribution makes them about the soft parts and life habits of the of great value in the subdivision of Late ammonoids. It is rare to find the biting Palaeozoic and Mesozoic time. As a group, jaws, the tongue-like, rasping radula, or they are characterized by the position of the ink-sacs preserved in living chambers. Group: CLYMENIIDA Subgroup: CLYMENIIDAE Informal name: Clymeniid Clymenia limestone matrix The evolute shell has a wide, open umbilicus. It is either nearly smooth or it carries weak, gently curved growth lines. The whorl section is compressed, and the venter is rounded. The suture is very simple. HABITAT This genus lived a predatory existence on or near the floor of Devonian seas. REMARK One of the more primitive ammonoids, Clymenia was locally common in Late Devonian rocks, but not well preserved. Clymenia laevigata (M\u00fcnster); Late Devonian; Germany. broad umbilicus Typical diameter rounded venter 4cm (11\u20442in) Distribution: Europe, Asia, N. Africa Occurrence: Range: Late Devonian","142 | Invertebrates Group: CLYMENIIDA Subgroup: GLATZIELLIDAE Informal name: Clymeniid Soliclymenia simple, close ribs This is an unusually shaped ammonoid, evolute shell with a very evolute shell which shows form distinctive triangular coiling. It has a broad umbilicus and a rounded venter. The simple ribs are closely spaced; the suture is very simple. HABITAT It lived in moderately deep water. Although it could swim, its shell shape suggests it spent some time on the sea bed. Soliclymenia paradoxa (M\u00fcnster); Late Devonian; Germany. triangular coiling Typical length 2cm (3\u20444in) Distribution: Eurasia, N. Africa, N. America Occurrence: Range: Late Devonian Group: PROLECANITIDA Subgroup: PROLECANITIDAE Informal name: Goniatite Merocanites complex suture with deep folds The shell of Merocanites is evolute and has a broad, open umbilicus; Internal the profile is compressed, the sides mould parallel. The gently rounded flanks show a suture with several fine, dark, blade\u00adshaped folds (a fairly complex muddy form for Palaeozoic ammonoids). limestone The venter is rounded. matrix HABITAT Merocanites lived in Merocanites moderately deep water in the compressus Early Carboniferous seas. (J. Sowerby); REMARK The specimen is preserved Carboniferous in dark limestone as an iron-oxide- Limestone; coated internal mould. The living Early Carbon\u00ad chamber is not preserved. iferous, UK. Typical length 5cm (2in) Range: Early Carboniferous Distribution: Europe, Asia, N. America Occurrence:","Group: CERATITIDA Subgroup: CERATITIDAE Invertebrates | 143 Ceratites living\u00b7 Informal name: Ceratite chamber strong, The shell is moderately evolute with a broad umbilicus simple ribs and a flat venter. The sides bear strong, simple, widely suture spaced ribs, which end on the ventral margin in a tubercle. The closely spaced suture lines have a Ceratites nodosus highly distinctive form, with shallow, smoothly (Brugui\u00e8re); Triassic; rounded folds facing anteriorly, and toothed Germany folds facing posteriorly. Occurrence: HABITAT Ceratites lived in Informal name: Goniatite the shallow waters of the Triassic seas. Goniatites crenistria Phillips; Bowland Shales; limestone Early Carboniferous; UK. matrix narrow, Typical length Internal deep umbilicus 6cm (21\u20442in) mould Occurrence: Range: Triassic Distribution: Europe Group: GONIATITIDA Subgroup: GONIATITIDAE Goniatites The shell is strongly involute, with a small, narrow umbilicus. The suture includes both pointed and rounded elements in the form of a zigzag. The thin shell has an ornament of fine, closely spaced growth lines. HABITAT Goniatites lived in Carboniferous shelf seas, occurring locally in swarms over reef structures. The shape of its shell suggests that Goniatites was a poor swimmer. goniatitic suture line broad, rounded venter Typical length 6cm (21\u20442in) Range: Early Carboniferous Distribution: Worldwide","144 | Invertebrates AMMONITES AMMONITES ARE A FORM of ammonoid same time as other marine groups, such as distinguished by their complex suture belemnites, and terrestrial groups, such lines. They were abundant and diverse as dinosaurs. As both ammonites and all in the seas of the Mesozoic Era, and they their close relatives are extinct, scientists evolved very rapidly to produce numerous know very little about their mode of life. species and genera. After a decline in What is known about them has been diversity during the Late Cretaceous worked out mostly from experiments period, ammonites became extinct at the with model shells in water tanks. Group: PHYLLOCERATIDA Subgroup: PHYLLOCERATIDAE Informal name: Phylloceratid Phylloceras complex, frilled suture line A compressed, involute shell form and a distinctive frilly suture characterize the shells of these small to Polished medium-sized ammonites. They are either simply internal cast ornamented with growth lines or nearly smooth. The aperture is gently curved. Phylloceras sp.; Early Jurassic; HABITAT The fairly streamlined profile of the Mexico. shell, and the rounded venter, allowed this genus to swim at moderate Occurrence: speeds by jet propulsion. Informal name: Lytoceratid Typical diameter 10cm (4in) Lytoceras fimbriatus Range: Early Jurassic\u2013Late Cretaceous Distribution: Worldwide (J. de C. Sowerby); Group: LYTOCERATIDA Subgroup: LYTOCERATIDAE Middle Lias; Early Jurassic; UK. Lytoceras The shell of Lytoceras is evolute, with a wide umbilicus. The whorl section is evenly rounded. The shell is ornamented with fine, closely spaced ribs and less frequent flanges, which pass uninterrupted over the venter. The suture is complex. HABITAT The shell is ill-adapted for fast fine ribs Typical length swimming, and it may have lived near the 10cm (4in) bottom of the sea. REMARK Like Phylloceras (see above), Lytoceras is most abundant in low-latitude, deep-water deposits of the ancient Tethys Ocean. Range: Early Jurassic Distribution: Worldwide Occurrence:","Group: AMMONITIDA Subgroup: OXYNOTICERATIDAE Invertebrates | 145 Oxynoticeras living chamber Informal name: Ammonite broken away Internal cast in pyrites This distinctive ammonite is characterized by its strongly compressed, involute shell and knife-sharp keel. The suture line is complex and frilled. The lower specimen has been cut in half to show the septa (pyrite) and the cameral chambers, now filled with yellow calcite. The siphuncle is just visible next to the venter \u2013 its characteristic position. HABITAT The sharp keel would have offered minimum resistance to the water through which Oxynoticeras swam, and it is interpreted as one of the fastest-swimming ammonites of all. REMARKS The specimens are internal moulds in bronzy iron pyrites \u2013 a common ammonite mode of preservation in clays. Oxynoticeras oxynotum (Quenstedt); Lower Lias; Early Jurassic; UK. involute shell with small umbilicus cross-section of individual, nearly straight septa siphuncle just visible on ventral margin of shell chamber full of yellow calcite sharp keel Pyritized Typical diameter on margin of ammonite cut 10cm (4in) compressed in half Occurrence: shell Distribution: Worldwide Range: Early Jurassic","146 | Invertebrates Group: AMMONITIDA Subgroup: PSILOCERATIDAE Informal name: Ammonite Psiloceras grey shale matrix small individuals preserved as In many localities around the world, nacre shell this small, rather smooth genus is taken as the marker of earliest Jurassic time. The Psiloceratidae probably evolved from the Phylloceras group (see p.144) and retain rather simple sutures. The preservation of original deep pink, pearly shell, crushed flat in shale, is typical of fossil shells found in north Somerset, UK. HABITAT Psiloceras was a crushed shells moderately capable swimmer. REMARKS This genus was abundant locally in the Early Jurassic period. Typical diameter Psiloceras planorbis Occurrence: 7cm (23\/4in) (J. de C. Sowerby); Lower Informal name: Ammonite Lias; Early Jurassic; UK. Range: Early Jurassic simple Distribution: Worldwide S-shaped ribs Group: AMMONITIDA Subgroup: AMALTHEIDAE Brown sandstone Amaltheus mould Amaltheus is characterized by its very compressed, involute shell, and by the narrow keel which has an Occurrence: ornament resembling a piece of rope. The ornament of the flanks is weak and consists of sickle-shaped ribs or, more rarely, fine, spiral ribs. HABITAT The streamlined whorl profile and narrow keel suggest that it was quite a good swimmer. REMARKS The genus may have evolved from Phylloceras (see p.144). Amaltheus stokesi (J. Sowerby); Middle Lias; Early Jurassic; UK. Typical diameter compressed shell 7cm (23\/4in) with corded keel Range: Early Jurassic Distribution: Worldwide","Invertebrates | 147 Group: AMMONITIDA Subgroup: DOUVILLEICERATIDAE Informal name: Tractor Ammonite Douvilleiceras tubercles The shell is involute and compressed in profile. Strong, simple ribs pass over the rounded venter, and are each divided into numerous, even-sized tubercles, which would originally have carried short spines. HABITAT This genus was certainly simple ribs a poor swimmer \u2013 the broad profile umbilcus of the whorl offered considerable resistance to the water. Douvilleiceras may well have spent a lot of time scavenging or hunting on the sea bed. REMARK This well-preserved specimen from Madagascar has retained most of its original nacreous shell. Douvilleiceras Side View of inaequinodum view venter (Quenstedt); Early Cretaceous; Madagascar. Range: Early Cretaceous Distribution: Worldwide Typical diameter 10cm (4in) Group: AMMONITIDA Subgroup: PERISPHINCTIDAE Occurrence: Perisphinctes bifid ribs Informal name: Ammonite The shell is evolute exposing many whorls and a aperture wide shallow umbilicus. Finely spaced branching ribs pass over the rounded venter without venter interruption; there is no keel present. HABITAT Perisphinctes lived in warm shallow shelf seas and was probably a relatively slow swimmer. REMARKS This species and Douvilleiceras (above) are commercially mined for the fossil trade. Typical diameter Perisphinctes Side umbilicus View of 10cm (4in) (Dichotomoceras) view venter virguloides (Waagen); Late Jurassic; Madagascar. Occurrence: Range: Middle\u2013Late Jurassic Distribution: Worldwide","148 | Invertebrates Group: AMMONITIDA Subgroup: KOSMOCERATIDAE Informal name: Ammonite crushed Kosmoceras Kosmoceras duncani (J. de C. Sowerby); Oxford Clay; nacre shell This is a compressed, moderately Middle Jurassic; UK. evolute ammonite. It is very typical of Middle Jurassic deposits. The shell has a complex ornament of bunched ribs and rows of tubercles. The venter is narrow and flat. HABITAT Kosmoceras lived in deeper water and was probably a moderately good swimmer. REMARK The specimen is preserved in original shell material, crushed in shales. Typical diameter Distribution: Worldwide Occurrence: 6cm (21\/2in) Informal name: Ammonite Range: Middle Jurassic branching ribs evolute shell Group: AMMONITIDA Subgroup: PERISPHINCTIDAE form umbilicus Pavlovia This is a typical member of the abundant and widespread Late Jurassic family, Perisphinctidae. Members of the family are characterized by open, evolute shell forms, rounded whorl sections, and ornamentation of branching ribs. A long living chamber occupies nearly a whole whorl of the shell. The suture is complex. HABITAT This genus lived in the extensive Late Jurassic seas. Typical diameter Pavlovia 4cm (11\/2in) sp.; Upper Glauconite Series; Late Jurassic; Greenland. Range: Late Jurassic Distribution: Greenland, northern Europe Occurrence:","Group: AMMONITIDA Subgroup: DACTYLIOCERATIDAE Invertebrates | 149 Dactylioceras aperture carved Informal name: Ammonite \u201chead\u201d Dactylioceras The shell form is evolute, with many commune whorls visible, and a wide, shallow (J. de C. Sowerby); umbilicus. The fine, branching Upper Lias; ribs are closely spaced and Early Jurassic; UK. pass over a rounded venter. open-coiled, HABITAT Experiments have evolute form shown Dactylioceras to be a slow swimmer. REMARK In medieval times, ammonites were thought to be petrified snakes and were provided with carved heads for sale to pilgrims. fine, branching ribs Typical diameter rounded venter 7cm (23\/4in) Range: Early Jurassic Distribution: Worldwide Occurrence: Informal name: Ammonite Group: AMMONITIDA Subgroup: HILDOCERATIDAE short rostrum Harpoceras on aperture curved aperture This is a common Early Jurassic ammonite, characterized by a compressed, moderately sharp keel involute shell which bore a sharp ventral keel, and flanks with distinctive sickle-shaped sickle-shaped ribs. The aperture ribs was drawn into a short rostrum Occurrence: on the ventral margin. HABITAT This genus was probably a good swimmer, and fed by preying on small animals. REMARK The specimen is preserved as claystone coated with a thin layer of iron pyrites. Harpoceras falciferum (J. Sowerby); Upper Lias; Early Jurassic; UK. Typical diameter 12cm (43\/4in) Range: Early Jurassic Distribution: Worldwide","150 | Invertebrates Group: AMMONITIDA Subgroup: HILDOCERATIDAE Informal name: Ammonite Hildoceras sickle-shaped ribs interrupted Hildoceras had an evolute, laterally by groove compressed shell. The coarse, widely-spaced, sickle-shaped ribbing on the sides is wide umbilicus interrupted by a groove. The suture line is very complex. It has a very distinctive rectangular whorl section, which on the venter carries three low keels separated by two grooves. HABITAT Hildoceras was a moderate swimmer in the Early Jurassic shelf seas. REMARK This specimen is well preserved in a claystone nodule. Typical diameter Hildoceras bifrons triple-keeled 7cm (23\/4 in) (Brugui\u00e8re); Upper Lias; venter Early Jurassic; UK. Occurrence: Range: Early Jurassic Informal name: Ammonite Distribution: Europe, Anatolia, Japan Macroconch Group: AMMONITIDA Subgroup: EODEROCERATIDAE (female) Bifericeras larger body for egg In common with many ammonites, the larger production shell (macroconch) of Bifericeras is the female, and the smaller (microconch) is the male. Females required a larger body size for egg production and possible brooding habit. HABITAT Bifericeras lived in open seas of moderate depth, and either predated on or scavenged small marine invertebrates. Microconch (male) Range: Early Jurassic Bifericeras bifer Typical diameter (Quenstedt); Lower 3cm (11\/4in) Lias; Early Jurassic; UK. Occurrence: Distribution: Europe"]