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Devonian Period Shark

Paleontologists in Morocco have found fossil fragments from a previously undescribed genus and species of symmoriiform shark that lived during the Late Devonian epoch.

Ferromirum oukherbouchi reconstructed in association with invertebrates (orthocerid cephalopods and thylacocephalans) from the Devonian of Maider region, Morocco. Image credit: Frey et al., doi: 10.1038/s42003-020-01394-2.

Ferromirum oukherbouchi reconstructed in association with invertebrates (orthocerid cephalopods and thylacocephalans) from the Devonian of Maider region, Morocco. Image credit: Frey et al., doi: 10.1038/s42003-020-01394-2.

The newly-identified shark, Ferromirum oukherbouchi, swam in Earth’s oceans some 365 million years ago (Devonian period).

It had a slender body measuring about 33 cm (13 inches) in length, very large eyes and specialized jaws.

“The excellently preserved fossil we’ve examined is a unique specimen,” said senior author Dr. Christian Klug, a paleontologist in the Paläontologisches Institut und Museum at the University of Zurich.

Dr. Klug and his colleagues from Switzerland, the United States and the Netherlands investigated the morphology and biomechanics of the superbly preserved jaws of Ferromirum oukherbouchi.

“What we discovered in the process was that unlike in humans, the two sides of the lower jaw were not fused in the middle,” they said.

“This enabled the animals to not only drop the jaw halves downward but at the same automatically rotate both outwards.”

Ferromirum oukherbouchi: (a) photo and (b) line drawing of the specimen; (c) head region including parts of the rostrum, sclerotic ring, mandibular arch, hyoid arch, branchial skeleton and shoulder girdle in ventral view; (d) soft tissue remains, including liver and spiral valves; (e) pelvic and caudal region. Scale bars - 100 mm in (a, b) and 30 mm in (c-e). Abbrevations: chy – ceratohyal, cop – copula, cbr – ceratobranchials, fs - fin spine, liv – liver, mc - Meckel’s cartilage, p.pl - pelvic plate, pq – palatoquadrate, ros – rostrum, scl.r - sclerotic ring, scor – scapulocoracoid, stc - stomach content, spv - spiral valves. Image credit: Frey et al., doi: 10.1038/s42003-020-01394-2.

Ferromirum oukherbouchi: (a) photo and (b) line drawing of the specimen; (c) head region including parts of the rostrum, sclerotic ring, mandibular arch, hyoid arch, branchial skeleton and shoulder girdle in ventral view; (d) soft tissue remains, including liver and spiral valves; (e) pelvic and caudal region. Scale bars – 100 mm in (a, b) and 30 mm in (c-e). Abbrevations: chy – ceratohyal, cop – copula, cbr – ceratobranchials, fs – fin spine, liv – liver, mc – Meckel’s cartilage, p.pl – pelvic plate, pq – palatoquadrate, ros – rostrum, scl.r – sclerotic ring, scor – scapulocoracoid, stc – stomach content, spv – spiral valves. Image credit: Frey et al., doi: 10.1038/s42003-020-01394-2.

“Through this rotation, the younger, larger and sharper teeth, which usually pointed toward the inside of the mouth, were brought into an upright position,” added first author Dr. Linda Frey, also from the Paläontologisches Institut und Museum at the University of Zurich.

“This made it easier for animals to impale their prey.”

“Through an inward rotation, the teeth then pushed the prey deeper into the buccal space when the jaws closed.”

This mechanism not only made sure the larger, inward-facing teeth were used, but also enabled Ferromirum oukherbouchi to engage in what is known as suction feeding.

“In combination with the outward movement, the opening of the jaws causes sea water to rush into the oral cavity, while closing them results in a mechanical pull that entraps and immobilizes the prey,” the researchers said.

“We believe that the described type of jaw joint played an important role in the Paleozoic era.”

“With increasingly frequent tooth replacement, however, it became obsolete over time and was replaced by the often peculiar and more complex jaws of modern-day sharks and rays.”

The discovery of Ferromirum oukherbouchi was reported in a paper in the journal Communications Biology.

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L. Frey et al. 2020. A symmoriiform from the Late Devonian of Morocco demonstrates a derived jaw function in ancient chondrichthyans. Commun Biol 3, 681; doi: 10.1038/s42003-020-01394-2

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