Aquatic younginiforms with 5 nares

Three related taxa from the Middle Triassic,
Sinosaurosphargis (Fig. 1, Li, Rieppel, Wu, Zhao and Wang 2011), Atopodentatus (Fig. 2, Cheng et al. 2014, Chun et al. 2016) and Largocephalosaurus (Fig. 3, Cheng et al. 2012, Li et al. 2013) appear to have five nares in the rostrum. Only the middle pair are the real nares, homologous with those of other tetrapods. Apparently some of these were overlooked by prior workers. So were some of the sutures.

Figure 1. Sinosaurophargis skull from Li et al. 2011. Colors added here. Five nares in black. Note the overlooked upper temporal fenestrae and postorbitals. Here a crack was identified as a naris. The lacrimal was originally missing. Here it forms the largest portion of the rostrum.
Figure 2. Atopodentatus skuill from Chun et al. 2016. Colors added here. Five nares blink in dark gray. The lacrimal (tan) contacts the naris.
Figure 3. Largocephalosaurus skull from Li et al. 2013. Colors added here. Five nares blink in dark gray. Here the external naris (en) was overlooked and similar cracks were misidentified as nares.

The current review of the MacClade file
that built the large reptile tree (LRT, 2049 taxa) prompted reexamination of these three specimens. Turns out the diagrams provided by the authors did not have all the correct data when it came to identifying certain traits and errant scores resulted. If your cladogram is experiencing loss of resolution at certain nodes, go back and review the data. These three examples demonstrate published data sometimes require a review.

References
Cheng L, Chen X-H, Zeng X-W and Ca Y-J 2012. A new eosauropterygian (Diapsida: Sauropterygia) from the Middle Triassic of Luoping, Yunnan Province. Journal of Earth Science 23 (1): 33-40.
Cheng L, Chen XH,Shang QH and Wu XC 2014. A new marine reptile from the Triassic of China, with a highly specialized feeding adaptation. Naturwissenschaften. doi:10.1007/s00114-014-1148-4.
Chun L, Rieppel O, Cheng L and Fraser NC 2016. The earliest herbivorous marine reptile and its remarkable jaw apparatus. Science Advances 06 May 2016: 2(5), e1501659
DOI: 10.1126/sciadv.1501659
Li C, Rieppel O, Wu X-C, Zhao L-J and Wang LT 2011. A new Triassic marine reptile from southwestern China. Journal of Vertebrate Paleontology 31 (2): 303-312. doi:10.1080/02724634.2011.550368.
Li C, Jiang D-Y, Cheng L, Wu X-C and Rieppel O 2013. A new species of Largocephalosaurus (Diapsida:Saurosphargidae), with implications for the morphological diversity and phylogeny of the group.

wiki/Atopodentatus
wiki/Largocephalosaurus
wiki/Sinosaurosphargis

Advertisement

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.