The other Dimorphodon skull (BMNH R 1035) unscrambled

We know of
several Dimorphodon (Buckland 1829, Owen 1859) Hittangian, Early Jurassic ~195 mya) specimens from Europe.

  1. BMNH (NHUK PV) R1034a Mary Anning’s discovery and the holotype, a misarticulated skeleton lacking a skull and tail (Fig. 1)
  2. BMNH (NHUK PV) R 1035 includes a skull, cervicals and wings (Figs. 1, 2)
  3. BMNH 41212 is a nearly complete specimen lacking a tail (Fig. 1).
  4. BMNH? a complete tail (Fig. 1)
  5. Other BMNH specimens. presumably disarticulated bones
  6. YPM 350, YPM 9182 and other Yale specimens, several disarticulated bones including a partial skull

Dimorphodon? weintraubi (IGM 3494, Clark et al. 1994, 1998; Early to Middle Jurassic, ~175 mya) nests several nodes away, with basal anurognathids. It lived 20 million years later in North America.

Figure 1. The three most complete Dimorphodon specimens, BMNH 41212, BMNH R1034, and BMNH R1035.

Figure 1. The three most complete Dimorphodon specimens, BMNH 41212, BMNH R1034, and BMNH R1035. BMNH (British Museum of Natural History) used to be NHUK (Natural History United Kingdom).

The BMNH R1035 specimen of Dimorphodon
has not been figured very often because the skull is somewhat scrambled  Here it is traced (Fig. 2) and reconstructed (Fig. 1). It is quite similar to that of the BMNH 41212 specimen, with only slight modifications.

Figure 2. Dimorphodon specimen BMN R1035 with elements traced. Here the complete wing was recovered along with cervicals and occipital elements.

Figure 2. Dimorphodon specimen BMNH (formerly NHUK) R1035 with elements traced and segregated to reduce the chaos. Here the complete wing was recovered along with cervicals and occipital elements. Click to enlarge.

The ‘scrambled’ 1035 material differs
from the 41212 material in several traits:

  1. The naris is slightly larger relative to the antorbital fenestra
  2. The sclera ring is smaller
  3. The mandible is deeper
  4. The metacarpus and wing are longer

When you look up Dimorphodon online
at Wikipedia the authors do not identify D. weintraubi as an anurognathid. And they follow Clark et al. in asserting that Dimorphodon had plantigrade pedes based on the metatarsalphalangeal butt joint. We looked at that problem earlier here and Peters (2000) also covered that topic, but essentially the metatarsophalangeal butt joint was immobile, but the cylindrical interphalangeal joints provided the required extension to create a digitigrade pes that matches digitigrade pterosaur and Rotodactylus ichnites in which the proximal phalanges are always elevated. It’s a common pattern: Sometimes it takes the paleo crowed a long time to accept certain facts.

Figure 3. from Wikipedia, my sculpture of Dimorphodon now found in several museums. The curly-cue tail, anteriorly-planted fingers and plantigrade feet are all unnatural.

Figure 3. from Wikipedia, my sculpture of Dimorphodon now found in several museums. The curly-cue tail, anteriorly-planted fingers and plantigrade feet are all unnatural and not part of the original model.

And then, of course manual digit 5 and wing ungual
are both present in the 1035 specimen (Figs. 4, 5).

Figure 4. Wingtip ungual in the BMNH 1035 specimen of Dimorphodon.

Figure 4. Wingtip ungual in the BMNH 1035 specimen of Dimorphodon.

Yes, they are difficult to see
unless you look for them and trace them. But think how long it took to find hind limbs in fossil whales, known for over 150 years prior to that discovery.

Figure 5. Manus of the BMNH 1053 specimen of Dimorphodon highlighting vestigial digit 5 in pink.

Figure 5. Manus of the BMNH 1053 specimen of Dimorphodon highlighting vestigial digit 5 in pink.

A while back
Nesbitt and Hone 2010 attempted to show that the 41212 specimen of Dimorphodon had a mandibular fenestra in a desperate and misguided attempt at providing archosaur traits to pterosaurs. That was bogus, as noted earlier. Those two didn’t want to take into account the slipped surangular on the specimen. In the 1035 specimen the surangular is in place and no mandibular fenestra is present.

References
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Clark J, Montellano M, Hopson J and Fastovsky D. 1994. In: Fraser, N. & H.-D Sues, Eds. 1994. In the Shadows of Dinosaurs. New York, Cambridge: 295-302.
Clark J, Hopson J, Hernandez R, Fastovsk D and Montellano M. 1998. Foot posture in a primitive pterosaur. Nature 391:886-889.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods. – Ichnos 7(1): 11-41.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88

wiki/Dimorphodon

 

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