Paleontologists have described a new genus and species of broad-snouted chondrichthyan fish from several fossilized specimens found in Morocco.
Reconstruction of Maghriboselache mohamezanei in its habitat. Thylacocephalans, cephalopods with orthoconic conchs, placoderms such as Dunkleosteus and osteichthyans populated the water column during the middle Famennian in the Anti-Atlas of Morocco. Image credit: Klug et al., doi: 10.1186/s13358-023-00266-6.
The newly-identified species lived during the Famennian stage of the Late Devonian epoch, some 365 million years ago.
Dubbed Maghriboselache mohamezanei, the ancient fish was between 0.8 and 2.5 m (2.6-8.2 feet) long.
It belongs to the family Cladoselachidae and represents a sister taxon to the iconic genus Cladoselache.
“This family now comprises the genera Cladoselache and Maghriboselache, thus far limited to the Famennian of the United States and Morocco,” said lead author Dr. Christian Klug, a paleontologist with the Paläontologisches Institut und Museum at the University of Zurich, and his colleagues.
Several well-preserved skeletons of Maghriboselache mohamezanei were found in the southern parts of the Maïder Basin and of the Tafilalt Platform in the Moroccan Anti-Atlas.
“Maghriboselache mohamezanei is represented by several individuals, some of which include a three-dimensionally preserved neurocranium,” the paleontologists explained.
“These specimens, like those of other chondrichthyans from the eastern Anti-Atlas are nearly complete, nearly fully articulated and several examples include remains of the integument, musculature, digestive tract and the liver.”
“Along with many other chondrichthyans, this material was extracted from the Thylacocephalan layer (middle Famennian) of the highly fossiliferous Devonian marine sedimentary outcrops laid down in two small epicontinental basins, now located in the Maïder and Tafilalt regions of the eastern Anti-Atlas of Morocco.”
“Besides chondrichthyans, these sediments have also yielded diverse invertebrates, placoderms, acanthodian stem-chondrichthyans, and actinopterygians.”
Skeletons of Maghriboselache mohamezanei from eastern Anti-Atlas, Morocco. Image credit: Klug et al., doi: 10.1186/s13358-023-00266-6.
Maghriboselache mohamezanei had a broad snout and a widely separated and generously proportioned pair of nasal capsules.
This feature is unknown in other contemporary or subsequent Paleozoic sharks and might even be the earliest instance in all jawed vertebrates (gnathostomes).
“With Cladoselache, Maghriboselache mohamezane shares a highly distinctive tooth morphology (each tooth base includes a deep basolabial depression with adjacent projections), a characteristic upper jaw shape (the quadrate process is shorter than the palatine process), and specialized pectoral fin structure (supported by strap-like radials reaching the fin perimeter),” the scientists said.
“With symmoriiforms, it shares a high aspect ratio tail and a braincase with a narrow-waisted basicranium.”
“With holocephalans in general, it shares a braincase with a greater ethmosphenoid unit bearing large orbits and a shorter, compact, closed, otico-occipital unit.”
“But, Maghriboselache mohamezane is also set apart, distinguished from all other early sharks, by the possession of a spectacularly broad, cartilage-enclosed, snout with widely spaced, large nasal capsules — the earliest known example of such condition in the chondrichthyan and (perhaps) gnathostome record,” they said.
“This suggests sensory specialization approaching that of extant broad-rostrum elasmobranchs and represents a significant addition to increasingly apparent ecomorphological diversity among early chondrichthyans.”
The findings were published in the Swiss Journal of Palaeontology.
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C. Klug et al. 2023. Broad snouted cladoselachian with sensory specialization at the base of modern chondrichthyans. Swiss J Palaeontol 142, 2; doi: 10.1186/s13358-023-00266-6
