Arcticodactylus a tiny Greenland Triassic pterosaur

Arcticodactylus cromptonellus (Kellner 2015, originally Eudimorphodon cromptonellus Jenkins et al. 1999, 1999; MGUH VP 3393) Late Triassic ~210mya ~8 cm snout to vent length was a tiny pterosaur derived from a sister to Eudimorphodon ranzii and phylogenetically preceded Campylognathoides and BSp 1994 specimen attributed to Eudimorphodon. Whether it was a juvenile or a tiny adult cannot be determined because juveniles and even embryos are identical to adults in pterosaurs. Note that that rostrum was not shorter and the orbit was not larger than in sister taxa. This specimen is one of the smallest known pterosaurs., but not THE smallest (Fig. 1) contra the Wikipedia article. That honor goes to B St 1967 I 276.

Figure 1. Articodactylus is evidently NOT the smallest pterosaur. That honor still goes to an unnamed specimen (not a Pterodactylus kochi juvenile) B St 1967 I 276.

Figure 1. Articodactylus is evidently NOT the smallest pterosaur. That honor still goes to an unnamed specimen (not a Pterodactylus kochi juvenile) B St 1967 I 276.

Distinct from E. ranzii,
the skull of Arctiodactylus had a rounder, less triangular orbit. The jugal was not as deep. The sternal complex did not have small lateral processes. The humerus was not as robust. The fingers were longer an more gracile. The prepubis was distinctly shaped.

Distinct from
Bergamodactylus the femur and tibia were smaller but the metatarsals were longer, compact and nearly subequal in length with IV smaller than III.

References
Jenkins FA Jr, Shubin NH, Gatesy SM and Padian K 1999. A primitive pterosaur of Late Triassic age from Greenland. Journal of the Society of Vertebrate Paleontology 19(3): 56A.
Jenkins FA Jr, Shubin NH, Gatesy SM and Padian K 1999. A diminutive pterosaur (Pterosauria: Eudimorphodontidae) from the Greenlandic Triassic. Bulletin of the Museum of Comparative Zoology, Harvard University 155(9): 487-506.
Kellner AWA 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências 87(2): 669–689

wiki/Eudimorphodon
wiki/Arcticodactylus

Bergamodactylus wildi- a new name for the basalmost pterosaur, MPUM 6009

Finding higher resolution data
is always a delight. Here DGS and a reconstruction perhaps reveal more accurate data on a skull of a basal pterosaur than direct observation (Fig. 1). You decide.

Figure 2. Bergamodactylus skull colorized with DGS and reconstructed.

Figure 2. Bergamodactylus skull colorized with DGS and reconstructed.

Kellner (2015)
commented on several Triassic European pterosaurs. Among them, MPUM 6009 was originally described as a juvenile Eudimorphodon by Wild (1978) and later congeneric with the basal anurognathid, Carniadactylus by Dalla Vecchia (2009). Peters (2007) nested this specimen as the basalmost pterosaur, though this reference was not listed. Kellner (2015) reported “no indication that MPUM 6009 is a juvenile.” confirming the assessment here.

Bergamodactylus wildi
is the new name for MPUM 6009 a Late Triassic (Norian) basal pterosaur from Bergamo, Italy. Unfortunately the tracing of the specimen is very vague (Fig. 1). Both jugals are drawn as one and many bones are not identified. This is remedied by DGS, which not only identifies left and right bones, but enables an accurate reconstruction with all parts fitting as in other articulated pterosaurs. Note the twin anterior dentary extensions. Are those teeth? A keratin extension has been hypothesized for other basal pterosaurs. Part of the maxilla ascending process is broken and flipped but repaired above. The posterior process of the left postorbital is broken like a wishbone. Here (Fig. 1) it is repaired to resemble the right postorbital. The occiput is identified along with several hyoids that were overlooked earlier. Does the coronoid have a tall triangular process? Perhaps, but that could also be an ectopterygoid. We’ll have to see about that.

Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

Figure 2. Updated reconstruction of Bergamodactylus to scale with an outgroup, Cosesaurus. Compared to the cranium and declined quadrates, the face appears to be downturned. This only makes sense in a bipedal configuration, as shown.

References
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.) rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Kellner AWA 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências (2015) 87(2): (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225-233.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

wiki/Eudimorphodon

On the origins of Dimorphodon and Eudimorphodon

At the base of the Pterosauria
there was one false evolutionary start that gave us Austriadactylus (the Austrian specimen) and Raeticodactylus. Thereafter the clades kicked into full gear with the basal dichotomy, dimorphodontids (which begat anurognathids) and eudimorphodontids (which begat everything else.)

Knowing that a picture tells the story here are the players (Fig. 1):

The origins of Dimorphodon and Eudimorphodon find a common ancestor close to Austriadactylus (the Italian specimen) and prior to that, the basal pterosaur, MPUM 6009. All are Late Triassic except Dimorphodon. The robust skull of eudimorphodontids suggests piscatory (fish eating) while the fragile skulls of dimorphodontids suggests insectivore. The enlarged naris was a legacy from the Italian specimen

The origins of Dimorphodon and Eudimorphodon find a common ancestor close to Austriadactylus (the Italian specimen) and prior to that, the basal pterosaur, MPUM 6009. All are Late Triassic except Dimorphodon. The robust skull of eudimorphodontids suggests piscatory (fish eating) while the fragile skulls of dimorphodontids suggests insectivore. The enlarged naris was a legacy from the Italian specimen

The basic dichotomy of dimorphodontids and eudimorphodontids (Fig. 1) set the pace for the rest of pterosaur evolution. One emphasized the longer, leaner snout of a fish and tetrapod eater while the other had a taller, more fragile and ultimately wider rostrum (in anurognathids) of an insect eater.

You can see (Fig. 1) with such short fore limbs and long hind limbs, with toes under the center of balance at the shoulder glenoid (arm pit) that quadrupedal locomotion was something that would have to be invented in the future of these Triassic clades.

BTW
Yesterday’s note on Atopodentatus garnered about twice as many viewers. Let me know why all the interest because I don’t have a clue.