Sunday, December 6, 2020

Antarctic Ichthyornis solved

So I've been doing some major updates to the Database for what will probably be a New Years upload, including the ornithuromorph section. One rather sad entry as it currently stands is the Antarctic Ichthyornis

I? sp. (Zinsmeister, 1985)
Late Cretaceous
Seymour Island, Antarctica
- Zinsmeister, 1985. 1985 Seymour Island expedition. Antarctic Journal of U.S. 20, 41-42. 

Now with Googling I found the original paper online, which allowed only a bit of improvement-

I? sp. (Zinsmeister, 1985)
Late Maastrictian, Late Cretaceous
Lopez de Bertodano Formation, Seymour Island, Antarctica

Material- several elements
- Zinsmeister (1985) states "several small bones tentatively identified as belonging to the Cretaceous bird Ichthyornis were discovered in the upper Cretaceous Lopez de Bertodano formation." 
Reference- Zinsmeister, 1985. 1985 Seymour Island expedition. Antarctic Journal of U.S. 20, 41-42.

So I saw that Zinsmeister worked with Chatterjee in the 80s, who found the Polarornis holotype in the same place two years before that.  I emailed Chatterjee about it, who replied-

"It was misidentified in the field. These were some shark teeth."

Mystery solved!  But can we do better?  Here's an Ichthyornis tooth-

Right eleventh dentary tooth of Ichthyornis dispar (YPM 1450) (after Field et al., 2018).

And here's the array of shark teeth from the Lopez de Bertodano Formation of Seymour Island (from a January 2011 expedition).  Can we find any easily confusable matches?

Chondrichthyan teeth from the Lopez de Bertodano Formation (scale 10 mm) (after Otero et al., 2014).

I think the circled 16 and 17 are pretty decent matches for a field identification, though much larger if compared directly.  Figures 6-17 are all identified as Odontaspidae indet., which covers any morphology similar to Ichthyornis.  Add in the fact that they were by far the most abundant teeth recovered (8 samples versus 1-3 for the other taxa), and I think we have a nice solution on our hands.

I wonder how many other weird records are out there that are based on initial misidentification but stay in the literature because nobody ever publishes a correction?

References- Otero, Gutstein, Vargas, Rubilar-Rogers, Yury-Yañez, Bastías and Ramírez, 2014. New chondrichthyans from the Upper Cretaceous (Campanian-Maastrichtian) of Seymour and James Ross islands, Antarctica. Journal of Paleontology. 88(3), 411-420.

Field, Hanson, Burnham, Wilson, Super, Ehret, Ebersole and Bhullar, 2018. Complete Ichthyornis skull illuminates mosaic assembly of the avian head. Nature. 557, 96-100.


  1. "I wonder how many other weird records are out there that are based on initial misidentification but stay in the literature because nobody ever publishes a correction?"

    You mean like Protoavis? ;-) Any chance Sankar Chatterjee will publish a revised taxonomic description of this one?

    1. Sort of, but at least we have Witmer (2001) for Protoavis. In any case, my next blog post is going to cover these kinds of cases...

  2. Witmer (2001) provides a very measured and objective review of the Protoavis material, and features this cogent understatement:
    "But, without question, the most vexing problem is that Chatterjee's descriptions tend to be of the reconstructions, not of the actual fossils, in effect denying the reader the opportunity to reach his or her own conclusions."
    Unless the epoxy/plaster can be distinguished from the authentic fossil material, identifying many Protoavis elements might be a forlorn cause.

    1. Mickey Mortimer considers putative sternal arm, and hand elements assigned the Protoavis holotype and paratype (as well as putative lower forelimb remains from the Tecovas Formation referred to Protoavis by Chatterjee 1995) to belong to one of two as-yet-unnamed taxa described in Atanassov (2002) as belonging to close relatives of pterosaurs. Chatterjee's (1991) interpretation of Protoavis as having opisthopuby is tenuous because the ancestral avialan definitely had a propubic pelvis.

      Chatterjee (1991) based his reconstructions of Protoavis on his interpretation of morphological features of the holotype and paratype. You have to remember that at the time the paper naming Protoavis was being scripted, knowledge about Mesozoic birds from the Berriasian-early Albian interval was virtually minimal with the exception of the Asian bird Gansus from the Barremian and Noguerornis
      from Spain. We now know, however, from discoveries of avialan fossils from the Middle Jurassic to Middle Cretaceous of East Asia that morphological features that Chatterjee (1991, 1997) interpreted as tying Protoavis to ornithuromorphs don't reflect the ancestral condition of Avialae.

    2. IRRC, Atanassov's taxa were called 'Pteromimus' and 'Procoelosaurus', both nomina nuda.

      This undescribed material deserves even more scrutiny in light of today's Nature paper (Ezcurra et al.) on Lagerpetidae being the sister clade of Pterosauria.