Eosipterus – what is it?

There are two “headless” specimens
of Eosipterus yangi (lower Yixian Fm.) known to science (Lü et al. 2006, Fig. 1). Unfortunately, phylogenetic analysis indicates they are not congeneric. Lü et al. (2006) examined the referred specimen (D2514) and correctly nested it with ctenochasmatids. The holotype (Ji and Ji 1997, GMV2117) was originally considered an archaic “pterodactyloid” based not on analysis but on a lack of a tail and elongated metacarpals. Here, in the large pterosaur tree, it nests with germanodactylids.

The quality of the original specimen
and the lack of attention to detail prevented a great deal of data from becoming established. In the holotype, surprisingly, the head is preserved beneath the torso (Figs. 5, 6). The neck is bent back in an extreme death pose.

Similarly, much was missed in the referred specimen.
It is unfortunate that, despite their strong differences, these two specimens were both considered Eosipterus. The ctenochasmatid now needs a new genus and species. I would suggest Deneosipterus (=”not” Eosipterus).

Two other specimens are known
from private collections according to J-C Lü (correspondence), who wanted me to create artwork of a living Eosipterus. He sent me hirez images to work from. Previously I did not know about the referred specimen and the holotype was known to me by a very low rez image.

Note: I have not seen either specimen. Data gains from the original interpretations are due to more precise tracing using the DGS method (Photoshop) mentioned earlier.

Figure 1. Click to enlarge. The holotype of Eosipterus and the referred specimen.

Figure 1. Click to enlarge. The holotype of Eosipterus (right) and the referred specimen (left) to scale. These two don’t appear to be congeneric and they don’t nest together in phylogenetic analysis. The wide gastralia would certainly curve, but they also indicate a wide belly.

The diagnosis of Lü et al,
“includes the wing span is less than 1.25 meters, the length of the ulna is nearly equal to these of wing phalanx 2 and the tibia, humerus is longer than tibia, and the ratio of metatarsal to tibia is approximately 0.40.”

Figure 2. Eosipterus referred specimen D2514 as observed by Lü et al. 2006

Figure 2. Eosipterus referred specimen D2514 as observed by Lü et al. 2006. Not much detail here. Note the humerus is shorter than the tibia, even in their own drawing.

Diagnosis problems
The wingspan trait is found among dozens of pterosaurs. The ulna/m4.2 trait is present here, but also widespread among pterosaurs. The humerus is not longer than the tibia in either specimen (I’m guessing Lü et al. meant “shorter,” but the ratio continues throughout the text). The ratio of metatarsal to tibia is present here and also widespread.

Figure 2. Eosipterus referred specimen D2514 in situ.

Figure 3. Eosipterus referred specimen D2514 in situ. Medium red represents wing membrane

D2514
What Lü et al. (2006) identified as two scapulae are the clavicles, part of the triangular sternal complex. What Lü et al. (2006) identified as the last two cervicals are actually cervicals 6 and 7. Cervical #8 was not identified, but is visible. This specimen nests with early ctenochasmatids.

GMV 2117
The Eosipterus holotype nests with germanodactylids like the BMM specimen and the JME specimen, but has a much smaller skull than either. The skull in

Figure 4. The holotype of Eosipterus as originally figured by Ji and Ji 1997. The skull shown here was completely imagined. They thought the skull, cervicals and pectoral girdle were not preserved.

Figure 4. The holotype of Eosipterus as originally figured by Ji and Ji 1997. The skull shown here was completely imagined. They thought the skull, cervicals and pectoral girdle were not preserved.

Figure 3. Eosipterus holotype GMV 2117 preserves wing and uropatagial impressions.

Figure 5. Eosipterus holotype GMV 2117 preserves wing and uropatagial impressions like those of other pterosaurs, narrow chord throughout. Coracoids are purple. Scapulae are orange. Humeri are deep blue. Sternal complex is pink (sternum), light blue (clavicles), and interclavicle (aqua).

Congeneric and conspecific?
Evidently the similar sizes and poses of the insitu specimens suggested they were congeneric. Reconstructions were not attempted for either description. The mistaken identity is the unfortunate result. Even the largest bones indicate separate derivation, but this doesn’t really become readily apparent until reconstructions are put side-by-side (Fig. 1).

D = Dalian Natural History Museum, Dalian, Liaoning, China
GMV = National Geological Museum of China, Beijing, China

References
Lü J-C, Gao C-L, Meng Q-J, Liu J-Y, Ji Q 2006. On the Systematic Position of Eosipterus yangi Ji et Ji, 1997 among Pterodactyloids. Acta Geologicia Sinica 80(5):643-646.
Ji S-A and Ji Q 1997. Discovery of a new pterosaur in Western Liaoning, China. Acta Geologica Sinica 71(1): 1-6 [in Chinese].
Ji S-A, Ji Q and Padian K 1999. Biostratigraphy of new pterosaurs from China. Nature 398: 573-574
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. In: Buffetaut E. & J-M. Mazin, Eds. Evolution and Palaeobiology of Pterosaurs. London, Geological Society Special Publication 217: 139-190.
Unwin DM, Lü J and Bakhurina NN 2000. On the systematic and stratigraphic significance of pterosaurs from the Lower Cretaceous Yixian Formation (Jehol Group) of Liaoning, China. Mitteilngen der Museum für Naturkunde in Berlin, Geowissenschftlichen Reihe 3: 181-206.

wiki/Eosipterus

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