44 Paleontology, Paleoecology/Taphonomy, Phylogenic Morphological Patterns (Posters)

Tuesday, 24 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Some Jurassic (Callovian) brachiopods from Gebel El-Minshera, northern Sinai and the paleoecologic significance of the apical angle

Paper number: 44-8
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Three brachiopod species, Bihenithyris marianae, Somalithyris briani and Goliathyris lewyi have been identified from the Jurassic (Upper Callovian) of Gebel El-Minshera, northern Sinai. The shells were collected on a slope of bioclastic limestone with the following associated cephalopod fauna: Pachyerymnoceras and Paracenoceras prohexagonum. These ammonites from the Lamberticeras lamberti Zone, found with the brachiopod shells indicate an Upper Callovian age. Workers have studied the relationship between the apical angle, functional morphology and paleoecology in brachiopods. For example, if a sharper apical angle is associated with an erect ventral beak, which implies a large, unobstructed delthyrium and a strong pedicle, does that reflect the sedimentary environment? Canadian workers (Jin and Copper, 2004) noted that it remains poorly understood whether the reduction of apical angles in their species populations of the brachiopod Stegerhynchus from Anticosti Island was of any paleoecological significance. They stated that in terms of functional morphology, a sharper apical angle is usually associated with an erect ventral beak, which in turn implies a large, unobstructed delthyrium and a strong pedicle. In contrast, a strongly obtuse apical angle is associated with an incurved ventral beak that is appressed to the dorsal umbo, resulting in the delthyrium being partly obscured. This would imply that such shells had a thin or weak pedicle, at least at their adult growth stage. Specimens of Bihenithyris from Jebel Tuwaiq, Saudi Arabia have smaller apical angles (range: 47°-77°) whereas the shells from Gebel El-Minshera, northern Sinai have apical angles ranging from 86°-97°. This may represent an evolutionary trend, but more work is needed to determine the sedimentary environment of the specimens from northern Sinai. It should be noted, however, that the size of the pedicle foramen in the Saudi Arabian shells is considerably larger than those from northern Sinai possibly indicating a more turbulent environment.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411083

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