At the eudimorphodontid – dimorphodontid split in pterosaurs

In the Late Triassic: Step one.
Sometime after the origin of the most primitive pterosaur, Bergamodactylus (MPUM 6009, Figs 1–3) pterosaurs began a rapid radiation, exploring new niches as the first flying vertebrates – with new morphologies to match every nice.

A short backstory
Pterosaurs did not appear without precedent, as outdated university textbooks report.

Non-volant pterosaur precursors were bipedal flappers with a new pelvic arrangement that diminished the caudofemoralis flexors while increasing femoral adductors and extensors anchored on the prepubes and anterior ilium. That’s why pterosaurs have an attenuated tail, unlike archosaurs.

Pterosaur wings were secondary sexual traits, emphasizing the earlier flapping behavior in occasionally bipedal Cosesaurus (Figs 1–3). Nonvolant related taxa, like Longisquama (Fig 1) used other intriguing ploys (= extended dorsal plumes) to hype their sex appeal.

Figure 8. Taxa at the genesis of pterosaurs: Cosesaurus, Longisquama and Bergamodactylus. ” data-image-caption=”

Figure 8. Taxa at the genesis of pterosaurs: Cosesaurus, Longisquama and Bergamodactylus.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588-2.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588-2.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-31039″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588-2.jpg” alt=”Figure 8. Taxa at the genesis of pterosaurs: Cosesaurus, Longisquama and Bergamodactylus.” width=”584″ height=”435″ />

Figure 1. Taxa at the genesis of pterosaurs: Cosesaurus, Longisquama and Bergamodactylus.

Step two.
What happened next? Some Triassc pterosaurs became bigger (Fig 2) and some developed a rostral crest (Fig 2) when flapping wings were no longer enough to impress the opposite gender. Being different was sexy.

In so many ways like this pterosaurs converged with birds.

Figure 2. Click to enlarge. Fenestrasaurs and Triassic pterosaurs, including Austriadactylus and Raeticodactylus. ” data-image-caption=”

Figure 2. Click to enlarge. Fenestrasaurs and Triassic pterosaurs, including crested Austriadactylus and Raeticodactylus.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/fenestrasaurs588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/fenestrasaurs588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-87893″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/fenestrasaurs588.jpg” alt=”Figure 2. Click to enlarge. Fenestrasaurs and Triassic pterosaurs, including Austriadactylus and Raeticodactylus.” width=”584″ height=”168″ />

Figure 2. Click to enlarge. Fenestrasaurs and Triassic pterosaurs, including crested Austriadactylus and Raeticodactylus.

Step three.
In the Late Triassic pterosaurs had a phylogenetic split dividing the dimorphodontids from the eudimorphodontids (Fig 3). Dimorphodontids ultimately evolved into anurognathids then disappeared in the earliest part of the Cretaceous. Eudimorphodontids evolved into all other pterosaurs, then disappeared at the last day of the Cretaceous.

Figure 1. Pterosaur taxa at the eudimorphodontid – dimorphodontid split to scale. ” data-image-caption=”

Figure 1. Pterosaur taxa at the eudimorphodontid – dimorphodontid split to scale.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/eudimorphodon-preondactylus588-1.jpg?w=84″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/eudimorphodon-preondactylus588-1.jpg?w=286″ tabindex=”0″ role=”button” class=”size-full wp-image-87891″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/07/eudimorphodon-preondactylus588-1.jpg” alt=”Figure 1. Pterosaur taxa at the eudimorphodontid – dimorphodontid split to scale.” width=”584″ height=”2088″ />

Figure 3. Pterosaur taxa at the eudimorphodontid – dimorphodontid split to scale.

Bergamodactylus wildi
(Wild 1978, Kellner 2015; MPUM 6009) Norian, Late Triassic, ~210 mya, was similar in size to Longisquama and was originally considered a juvenile Eudimorphodon ranzii. Later Dalla Vecchia (2009) considered this specimen congeneric with Carniadactylus, but the morphological differences are far too great. Often called “the Milan specimen” Bergamodactylus is a distinct taxon and the most primitive known pterosaur following the analysis of (Peters 2007) and that continues to the present day in the LRT and LPT.

Figure 2. Click to enlarge. Anurognathids to scale. The adult of the IVPP embryo is 8x the size of the embryo, as in all other tested adult/embryo pairings. ” data-image-caption=”

Figure 2. Click to enlarge. Anurognathids to scale. The adult of the IVPP embryo is 8x the size of the embryo, as in all other tested adult/embryo pairings.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/08/anurognathids588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/08/anurognathids588.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-48089″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/08/anurognathids588.jpg” alt=”Figure 2. Click to enlarge. Anurognathids to scale. The adult of the IVPP embryo is 8x the size of the embryo, as in all other tested adult/embryo pairings.” width=”584″ height=”245″ />

Figure 4. Click to enlarge. Anurognathids to scale. The adult of the IVPP embryo is 8x the size of the embryo, as in all other tested adult/embryo pairings.

There are 271 taxa
in the large pterosaur tree (LPT). Only a few basal taxa are shown here to tell the pterosaur Triassic tale.

Basal members of the Eudimorphodontia. ” data-image-caption=”

Figure 3. Click to enlarge. Basal members of the Eudimorphodontia.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/07/eudimorphodontia5881.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/07/eudimorphodontia5881.jpg?w=584″ tabindex=”0″ role=”button” class=”size-full wp-image-730″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/07/eudimorphodontia5881.jpg” alt=”Basal members of the Eudimorphodontia.” width=”584″ height=”265″ />

Figure 5. Click to enlarge. Basal members of the Eudimorphodontia.

Step 4.
In their fourth and final transformation(s) several pterosaur clades convergently developed pterodatyloid-grade traits: reducing their tail, reducing pedal digit 5, elongating metacarpal 4. Som experienced phylogenetic miniaturization, becoming about the size of the smallest hummingbird before descendants grew to the size of a moa.

Several pterosaurs eventually became flightless when other traits came to dominate attraction within species.

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.
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/Bergamodactylus