First Rhamphorhynchus from Gondwana (Chile)

This is exciting news.
Rhamphorhynchus is known chiefly from Solnhofen Limestones (Tithonian, 150mya). This specimen is from the earlier Oxfordian (160mya) in the Atacama Desert of northern Chile, formerly a coast of Gondwana.

Figure 1. Three views of the Gondwana humerus together with comparative taxa on frame Alarcon-Munoz et al. 2021. On frame two elements are two scale with a matching specimen, though half size, YPM 1778.
Figure 1. Three views of the Gondwana humerus together with comparative taxa on frame #1 of this figure from Alarcon-Munoz et al. 2021. The authors sprinkle those three views: A, H and K on this graphic. On frame #2 the same elements are shown ‘to scale’ and arranged according to genus. All three tracings of the Gondwana humerus are collected together and boxed at upper left. Added to frame #2 is a more closely matching specimen, YPM 1778, overlooked by the authors. It is half the size of the Chilean specimen. Two frames change every 5 seconds.

From the abstract:
“We describe partial remains of a non-pterodactyloid pterosaur from Upper Jurassic levels of the Atacama Desert in northern Chile. The material includes a left humerus, a possible dorsal vertebra, and the shaft of a wing phalanx, all preserved in three dimensions and likely belonging to a single individual. The humerus has a hatchet-shaped deltopectoral crest, proximally positioned, and its shaft is markedly anteriorly curved, which are characteristic features of the clade Rhamphorhynchidae.

Three views of the Chilean humerus
were provided by Alarcón-Muñoz et al. (Fig. 1) together with cherry-picked humeri of various Rhamphorhynchus and Dorygnathus specimens. In frame 2 (Fig. 1) these are also shown to scale, flipped to a common view (deltopectoral crest left) rearranged generically. Unfortunately the authors did not include the specimen with the humerus presently closest to the Gondwana specimen: the YPM 1778 specimen (n33 in Wellnhofer’s 1975 catalog) of Rhamphorhynchus shown here in situ (Fig. 2).

Figure 1. The Yale specimen of Rhamphorhynchus phyllurus with preserved wingtip ungual highlighted. See figure 2 for closeup.
Figure 2. The Yale specimen (YPM 1778) of Rhamphorhynchus phyllurus with preserved wingtip ungual highlighted. This humerus of this specimen is a close match to the Chilean humerus, but half the size.

From the abstract, continued:
In addition, the presence of a groove that runs along the caudal surface of the phalanx, being flanked by two asymmetric crests, is a distinctive feature of the clade Rhamphorhynchinae, which includes such genera as Rhamphorhynchus and Nesodactylus.

In the LRT Nesodactylus nests within Campylognathoides prior to the genesis of Rhamphorhynchus, which first appeared following phylogenetic miniaturization (Fig. 3).

“Previous to this research, known records of Rhamphorhynchinae were restricted to Laurasia; thus, the specimen studied here represents the first evidence of this group found to date in Gondwana. Associated ammonoids allow us to assign the material to a middle Oxfordian age, which makes this specimen the oldest known pterosaur found in Chile, and the first of Oxfordian age in Gondwana. This discovery suggests that the clade Rhamphorhynchidae had a global distribution during the Late Jurassic.”

Figure 2. Rhamphorhynchus specimens to scale. The Lauer Collection specimen would precede the Limhoff specimen on the second row.
Figure 3. Rhamphorhynchus specimens to scale. Click here to enlarge.

Global distribution for Rhamphorhynchus is excellent news,
and serves to emphasize the pure luck we have with fossil formation and fossil discovery. Fossil beds and localities can be extremely tiny pinpricks on the surface of the Earth. Even so, the LRT documents no large gaps in the fossil record. All included taxa look like close relatives.

Figure 4. Portion of the Rudolph Zallinger mural at the Yale Peabody Museum featuring Morrison Formation dinosaurs of North America and a European Rhamphorhynchus at upper left. The Gondwana Rhamphorhynchus makes this hypothesis of association more likely.

Alarcón-Muñoz J, et al (5 co-authors) 2021. First record of a Late Jurassic rhamphorhynchine pterosaur from Gondwana. Acta Palaeontolgica Polonica 66:
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.


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