Early Cretaceous NGMC 2124 = GMV 2124 enters the LRT with Aorun

Cau 2024 reported,
“A specimen referred to Sinosauropteryx by Currie & Chen (2001), NGMC 2124 (Fig 1), differs in several features from the former and represents a distinct taxon (Longrich, 2002).

This specimen also has short feathery filaments on the back and base of the neck, but nothing on the tail, except at the base. So not for display in this case.

Phylogenetically this was an early appearance of any feathers,
but chronologically fully feathered Archaeopteryx was older and more derived. So this specimen was unchanged from a much earlier radiation with regard to pelage.

Figure 1. GMN 2124 aka NGMC 2124 in situ. Colors and reconstructions added here. Note the short metatarsal 3. This is not seen in other theropods. This morphology largely prevents flexion and extension of the proximal pedal phalanges. ” data-image-caption=”

Figure 1. GMN 2124 aka NGMC 2124 in situ. Colors and reconstructions added here. Note the short metatarsal 3. This is not seen in other theropods. This morphology largely prevents flexion and extension of the proximal pedal phalanges.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/04/gmv2124.theropod588.jpg?w=139″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/04/gmv2124.theropod588.jpg?w=475″ class=”size-full wp-image-85570″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/04/gmv2124.theropod588.jpg” alt=”Figure 1. GMN 2124 aka NGMC 2124 in situ. Colors and reconstructions added here. Note the short metatarsal 3. This is not seen in other theropods. This morphology largely prevents flexion and extension of the proximal pedal phalanges.” width=”584″ height=”1258″ />

Figure 1. GMN 2124 aka NGMC 2124 in situ. Colors and reconstructions added here. Note the short metatarsal 3. This is not seen in other theropods. This morphology largely prevents flexion and extension of the proximal pedal phalanges. The black lines indicate PILs in distal phalanges are continuous for flexion and extension there.  This specimen is 1m long.

Cau 2024 also reported,
“Another, yet unnamed Jehol Biota “compsognathid” (NGMC 2124, originally referred
to Sinosauropteryx), has been placed among the earliest branches of Tyrannosauroidea.”

The large reptile tree (LRT, 2319 taxa) largely confirms this nesting, but nests this taxon a little further outside, more primitive.

BTW, Ji and Ji 1997b originally described this specimen, naming it another Sinosauropteryx. The name needs to change, but that does not mean it is ‘unnamed.’

Afterward 1997 several authors (see below) continued to name this specimen Sinosauropteryx prima, even though it does not nest with the holotype (in the LRT) and differs in many ways, confirming the assessment of Cau 2024.

Does anyone else know of another specimen
in which metatarsal 3 is shorter than mt2 and mt4 in theropods? I had a hard time trying to  figure this out, but both metatarsal sets share this odd-to-unique pattern. So it’s not an artifact of jumbled taphonomy. Such a morphology would have prevented flexion and extension of the proximal pedal phalanges. However more distally the medial set of parallel interphalangeal lines (PILs) dominates and is continuous across all three digits. So this novel morphology works for GMV 2124. It’s just different.

Two small Mesozoic cynodont jaws were described inside the gut
of GMV 2124 by Hurum  et al in 2006 highlighted here (Fig 2). Sinobaatar is an Early Cretaceous placental mutiturberculate. Zhangeotheriumi s am Earliest Cretaceous pre-mammal cynodont close to Maotherium and Yanaconodon in the LRT.

Figure 1. Stomach contents of NGMC2124 include jaw elements from two small Jurassic mammals. ” data-image-caption=”

Figure 1. Stomach contents of NGMC2124 include jaw elements from two small Jurassic mammals.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/04/ngmc2124stomach_contents588.jpg?w=300″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/04/ngmc2124stomach_contents588.jpg?w=584″ class=”size-full wp-image-85578″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/04/ngmc2124stomach_contents588.jpg” alt=”Figure 1. Stomach contents of NGMC2124 include jaw elements from two small Jurassic mammals.” width=”584″ height=”579″ />

Figure 2. Stomach contents of NGMC2124 include jaw elements from two small Jurassic mammals, described by Hurum, Luo and Kielan-Jaworska 2006,

A kind reader or two asked for Coelurus to be added to the LRT.
Unfortunately, not enough is currently known to make that happen. It needs skull, foot  and pelvis data that is currently lacking. Hopefully this much more complete taxon, NGMC 2124, will suffice.

References
Cau A 2024. A Unified Framework for Predatory Dinosaur Macroevolution. Bollettino della Società Paleontologica Italiana, 63(1): 1-19.
Currie PJ and Chen PJ 2001.Anatomy of Sinosauropteryx prima from Liaoning, northeastern China. Canadian Journal of Earth Sciences, 38: 705-727.
Hurum JH, Luo Z-X and Kielan-Jaworowska 2006. Were mammals originally venomous? Acta Palaeontologica. Polonica 51 (1): 1–11.
Ji Q and Ji,S-A1997b. Advances in the study of the avian Sinosauropteryx prima. Chinese Geology, 242: 30–32 (in Chinese).

wiki/Sinosauropteryx