Rib Displacement

Deformity. A displacement to the sculpture of the ammonite shell, resulting in the conspicuous displacement of the ribs (Fig. 16.14a-c), classified by Hengsbach (1979) as forma aegra syncosta, and illustrated by Keupp (1973), Landman and Waage (1986), and Bond and Saunders (1989).

Cause. Most likely, the result of a bite that caused fracturing and displacement of the shell. This deformity has also been observed in present-day Nautilus (see Ward, 1987).

Fig. 16.14 (a) Kosmoceras, injury showing rib displacement (BHI-5599) (xl). (b) Prorsiceras with an injury, showing displacement on the venter(BHI-5602) (xl.2). (c) Rurciceras (?) showing damage to the venter BHI-5601) (xl).

Fig. 16.15 (a) Quenstedtoceras (L.) lamberti with repaired injury (BHI-5415) (xl). (b) Grossouvria with repaired bite (BHI-5427) (xl). (c) Q. (L.) lamberti showing deformed whorl from a bite (BHI-5426) (xl). (d) Eboraciceras showing a deep groove and healed shell (BHI-5608) (x0.8). (e) Q. (L.) lamberti with displaced shell (BHI-5432) (x0.7). f) Q. (L.) lamberti showing healed injury as rib repair (BHI-5434) (x0.9).

Fig. 16.15 (a) Quenstedtoceras (L.) lamberti with repaired injury (BHI-5415) (xl). (b) Grossouvria with repaired bite (BHI-5427) (xl). (c) Q. (L.) lamberti showing deformed whorl from a bite (BHI-5426) (xl). (d) Eboraciceras showing a deep groove and healed shell (BHI-5608) (x0.8). (e) Q. (L.) lamberti with displaced shell (BHI-5432) (x0.7). f) Q. (L.) lamberti showing healed injury as rib repair (BHI-5434) (x0.9).

Fig. 16.16 (a) Quenstedtoceras (L.) lamberti, showing "spiral" scarring (BHI-5420) (xl). (b) Peltoceras, with rib displacement at the point ofinjury(BHI-5610) (xl.2). (c) Q. (L.) lamberti with a spiral scar along with scars from previously attached epizoa (BHI-5609) (xl.2). (d) Cadoceras exhibiting a healed groove with rib displacement at the point of injury (BHI-5604) (x0.8). (e) Recent Nautilus showing similar scarring from a healed bite (BHI-5611) (x0.3). (f) Recent Nautilus showing"spiral" scarring, and the point of injury (BHI-5612) (x0.2).

Fig. 16.16 (a) Quenstedtoceras (L.) lamberti, showing "spiral" scarring (BHI-5420) (xl). (b) Peltoceras, with rib displacement at the point ofinjury(BHI-5610) (xl.2). (c) Q. (L.) lamberti with a spiral scar along with scars from previously attached epizoa (BHI-5609) (xl.2). (d) Cadoceras exhibiting a healed groove with rib displacement at the point of injury (BHI-5604) (x0.8). (e) Recent Nautilus showing similar scarring from a healed bite (BHI-5611) (x0.3). (f) Recent Nautilus showing"spiral" scarring, and the point of injury (BHI-5612) (x0.2).

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