Saturday, 19 January 2013

New species of Devonian Tetrapod from the northeast of Greenland.

Tetrapod is a term used to describe the four-legged Vertebrates, i.e. Amphibians, Reptiles, Birds and Mammals (it includes Vertebrates thought to have descended from four-legged ancestors, but which now lack all the limbs). It also includes the group of Palaeozoic Fish from which modern Tetrapods descend, animals in which the Tetrapod body configuration, comprising four limbs supported a pelvic and pectoral girdles and a skull separated from the pectoral girdle by a distinct neck, had emerged, but yet which were clearly still fully aquatic Fish.

In a paper published in the January 2012 edition of the journal Palaeontology, Jennifer Clack of the University Museum of Zoology at the University of Cambridge, Per Ahlberg and Henning Blom of the Department of Organismal Biology at Uppsala University and Sarah Finney of the Sedgwick Museum at the University of Cambridge, describe a new species of Tetrapod Fish from the Late Devonian of northeastern Devonian. The species is described on the basis of specimens collected in the 1930s and 1940s, which  have remained undescribed in the collection of the Geological Museum in Copenhagen until now.

The new species is named Ymeria denticulata, where Ymeria refers to Ymer Island, off the northeast coast of Greenland, where the specimens were found, and denticulata refers to the fact that it has teeth on its prearticular, a bone in the back of its jaw. The species is described on the basis of two partial specimens, both of the lower jaw. The post-cranial skeleton is unknown, the species being assigned to the Tetrapoda due to its close resemblance to the better known Ichthyostega.

(Top) Photograph of the first specimen of Ymeria denticulata, in ventral view. Scale bar is 10 mm.  (Bottom) interpretive drawing of (Top) Clack et al. (2012)


(Top) Photograph of the first specimen of Ymeria denticulata, in dorsal view. Scale bar is 10 mm.  (Bottom) interpretive drawing of (Top) Clack et al. (2012)

(Top) Photograph of the second specimen of Ymeria denticulata, in lateral view. Scale bar is 10 mm.  (Bottom) interpretive drawing of (Top) Clack et al. (2012)

2 comments:

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  2. Sorry, Joe, it's not a fish, it's an aquatic tetrapod. What Jenny has been working on for the past couple of decades is the fish-tetrapod transition and I'm pretty sure she'd want to maintain the distinction.

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