New Species of Fossil Hybodontiform Shark Identified in Japan

Paleontologists in Japan have described a brand unique species of shark-admire cartilaginous fish in step with the fossilized teeth from the Gradual Triassic Momonoki Formation.

The fossilized teeth of Parvodus ominechonensis. Scale bars - 0.5 mm. Represent credit: Breeden III et al., doi: 10.1080/02724634.2024.2322749.

The fossilized teeth of Parvodus ominechonensis. Scale bars – 0.5 mm. Represent credit: Breeden III et al., doi: 10.1080/02724634.2024.2322749.

Named Parvodus ominechonensis, the newly-identified shark species lived correct thru the Gradual Triassic epoch, between 237 and 227 million years ago.

It belongs to Parvodus, a miniature genus of extinct hybodontiform sharks known from the Mesozoic Skills.

“Hybodontiformes is an extinct clade of sharks in total regarded as as to be the sister clade to Neoselachii (i.e., skates, rays, and fashionable sharks) internal the chondrichthyan clade Euselachia,” acknowledged Dr. Benjamin T. Breeden III from the Nationwide Museum of Nature and Science in Tsukuba and his colleagues.

“The earliest known unambiguous hybodontiform physique fossils are from the Mississippian, but remoted teeth lengthen the earliest records of the crew to the Gradual Devonian.”

“Hybodontiform fossils are known basically from coastal and lagoonal strata one day of the Gradual Paleozoic, suggesting that the ancestral paleoecology of the clade was once shallow marine.”

“Alternatively, some hybodontiforms it appears to be like changed into euryhaline early in the evolution of the clade, and from the Mississippian onward, hybodontiforms time and again invaded freshwater environments.”

“Hybodontiforms were essentially the most abundant sharks in every marine and non-marine vertebrate assemblages one day of the early Mesozoic, dwindling in diversity after the Early Jurassic till the extinction of the clade at or end to the cease of the Cretaceous.”

Life reconstruction of the hybodontiform shark Strophodus rebecae. Represent credit: Jorge Blanco / CC BY 4.0.

Life reconstruction of the hybodontiform shark Strophodus rebecae. Represent credit: Jorge Blanco / CC BY 4.0.

Several remoted teeth of Parvodus ominechonensis were quiet from the non-marine Momonoki Formation in the metropolis of Omine-chō (romanized Ominecho) in western Mine, Yamaguchi, Japan.

“A diversity of Triassic hybodontiforms is understood from Japan, but of these, Parvodus ominechonensis is the wonderful species known from non-marine deposits and the first reported occurrence of the family Lonchidiidae,” the paleontologists acknowledged.

Essentially based on the gaze, Parvodus ominechonensis fills a gap in the stratigraphic document of Parvodus between occurrences in Middle Triassic and Middle Jurassic layers.

“The realm Triassic document of Parvodus contains Parvodus huizodus from the Olenekian of China, Parvodus sp. from the Anisian of China, and Parvodus ominechonensis from the Carnian of Japan, of which Parvodus ominechonensis and Parvodus huizodus are known from non-marine deposits,” the authors acknowledged.

“After the Triassic, Parvodus is understood from marine and non-marine layers one day of Laurasia and in South The united states till its extinction correct thru the Early Cretaceous.”

“This means that Parvodus will have originated in freshwater habitats in the South China jam of Pangea following the cease-Permian mass extinction and a style of one day of the Triassic in conceal day East Asia sooner than attaining a world distribution later in the Mesozoic.”

The invention of Parvodus ominechonensis is reported in a paper in the Journal of Vertebrate Paleontology.

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Benjamin T. Breeden III et al. 2023. A novel freshwater lonchidiid hybodontiform shark (Chondrichthyes, Elasmobranchii) from the Upper Triassic Momonoki Formation in Yamaguchi, Japan. Journal of Vertebrate Paleontology 43 (5); doi: 10.1080/02724634.2024.2322749