Revised October 30, 2019 and November 4, 2019
as I revise the holotype specimen by deleting the limbs. The nesting does not change.
The basal bipedal crocodylomorph,
Gracilisuchus (Figs. 1-3), was one of the first taxa in the large reptile tree (LRT, 1592 taxa), back when there were about 260? taxa. At the time I used Romer’s 1972 reconstruction (Fig. 5) to score data points. That turned out to be a freshman mistake. Romer filled in the missing taxa with the so-called Tucuman specimen, PVL4597, but kept the hind limbs and feet from the holotype slab. The hips and tail are not preserved in the holotype specimen PULR8 (Fig. 1).
A larger cladogram problem.
Lecuona, Desojo and Pol 2017 report, “The phylogenetic relationships of G. stipanicicorum were evaluated based on an extensive phylogenetic analysis of Archosauriformes expanding a previous dataset (Nesbitt, 2011) in terms of both taxon and character sampling.” As we learned earlier in a 7-part series, the analysis by Nesbitt 2011 and all those that followed are flawed throughout. Those analyses include unrelated taxa and exclude pertinent taxa. When scores are corrected or filled in where appropriate the resulting topology closely matches the LRT.
Here’s a good idea:
Don’t trust ANY previously published cladograms. Build your own.
This revision gave me an opportunity to update the text
on the Gracilisuchus page. That was needed due to the large number of additional taxa added near Gracilisuchus over the last 8-9 years. With the loss of limbs data, the current nestings of Gracilisuchus and a headless taxon wrongly attributed (Lecuona and Desojo 2011) to Gracilisuchus, PVL4597, did not change with these corrections. Just goes to show, it’s the taxon list, not the character list, that is key to understanding hypothetical interrelationships.
reader Neil P for bringing Gracilisuchus back to my attention.
Butler RJ, Sullivan C, Ezcurra MD, Liu J, Lecuona A and Sookias RB 2014. New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and
the biogeography of the archosaur radiation. BMC Evolutionary Biology 14:1-16.
Lecuona A and Desojo, JB 2011. Hind limb osteology of Gracilisuchus stipanicicorum (Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 102 (2): 105–128.
Lecuona A, Desojo JB and Pol D 2017. New information on the postcranial skeleton of Gracilisuchus stipanicicorum (Archosauria: Suchia) and reappraisal of its phylogenetic position. Zoological Journal of the Linnean Society XX:1–40.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.