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New Perspectives on Pterosaur Palaeobiology volume

Monday, March 20, 2017 5:22
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(Before It's News)

The 2015 pterosaur meeting in Portsmouth, England
brings us several new papers. The meeting and abstracts were previewed here and reported on here by a participant.

From the intro: “The field of pterosaur research in palaeontology continues its rapid growth and diversification that began in recent decades. This volume is a collection of papers on these extinct flying reptiles that includes work on their taxonomy, behaviour, ecology and relationships.”

Oddly, the number of abstracts far exceeded the very few papers this time.

Palmer 2017 wrote:
“The preservation of the wing membrane of pterosaurs is very poor and the available fossil evidence does not allow its properties to be reconstructed. In contrast, the fossil record for the wing bones is relatively good and the advent of CT scanning has made it possible to build high-fidelity structural models of the wing spar. The bending strength of the wing spar of a 6 m wingspan ornithocheirid pterosaur is used to infer the likely membrane tension. The tensions required to suppress aeroelastic flutter and to minimize ballooning of the membrane under flight loads are also estimated. All three estimates are of similar magnitude and imply that the membrane must have contained high-modulus material, supporting the view that the reinforcing aktinofibrils were keratinous.”

Contra Palmer’s unfounded assertion, there are several specimens of pterosaurs that provide an excellent view of the wing membrane. For the most part wing shape designs continue to be stuck in the Dark Ages among several pterosaur workers with some actually flipping the wing tips. Those problems need to improve before further work on pterosaur wings.

Dalla Vecchia 2017 wrote:
“An incomplete bone from the latest Cretaceous dinosaur site of Villaggio del Pescatore (Trieste Province, Italy) is definitely a wing metacarpal of a pterodactyloid pterosaur. It represents the only Italian Cretaceous pterosaur remains known, as well as the only pterosaur from the Adriatic Carbonate Platform. With an estimated minimum length of 136 mm, it belongs to a relatively small individual relative to the standard of latest Cretaceous pterodactyloids. It is not as elongated and gracile as azhdarchid wing metacarpals and shows a mix of features found in Pteranodon and some more basal pterodactyloids. It is one of the very few remains of putative non-azhdarchid pterosaurs from the upper Campanian–Maastrichtian worldwide and supports the view that the Azhdarchidae were not the only pterosaur clade existing during latest Cretaceous times.”

Always good to see the gamut of pterosaurs increase.

Witton 2017 wrote:
“Understanding the ecological roles of pterosaurs is a challenging pursuit, but one aided by a growing body of fossil evidence for their dietary preferences and roles as food sources for other species. Pterosaur foraging behaviour is represented by preserved gut content, stomach regurgitates, coprolites and feeding traces. Pterosaurs being eaten by other species are recorded by tooth marks and teeth embedded in their fossil bones, consumer gut content and regurgitate, and their preservation entangled with predatory animals. This palaeoecological record has improved in recent years, but remains highly selective. The Jurassic rhamphorhynchid Rhamphorhynchus, Cretaceous ornithocheiroid Pteranodon and azhdarchid pterosaurs currently have the most substantial palaeoecological records. The food species and consumers of these taxa conform to lifestyle predictions for these groups. Rhamphorhynchus and Pteranodon ate and were eaten by aquatic species, matching expectations of these animals as sea-going, perhaps partly aquatic species. Possible azhdarchid pterosaur foraging traces alongside pterosaur tracks, and evidence that these animals were eaten by dinosaurs and Crocodyliformes, are consistent with hypotheses that azhdarchids foraged and lived in terrestrial settings. Fossil evidence of pterosaur palaeoecology remains rare: researchers are strongly encouraged to put specimens showing details of dietary preferences, foraging strategies or interactions with other animals on record.”

When Pteranodon is no longer considered an ornithocheiroid by ptero workers, I will celebrate.

Bennett and Penkalski 2017 wrote:
“Four specimens of the pterosaur Pteranodon exhibit patterns of irregular alternating light and dark bands on the lateral surfaces of the upper jaw anterior to the nasoantorbital fenestra. Examinations reveal that the maxilla and premaxilla of Pteranodon consisted of two thin sheets of bone interconnected by regularly spaced septa with the spaces contained within presumably pneumatized, resulting in a structure analogous to modern honeycomb sandwich panels. The alternating light and dark bands resulted from waves of bone deposition moving anteriorly along the external surface of the lateral sheet of bone and laying down thin laminae of new bone while bone was simultaneously resorbed from the internal surface of the lateral sheet to maintain its thickness. The specimens that exhibit the bands were immature males and no banding was found in mature specimens or immature females. Therefore, the presence of the bands in immature males is interpreted as correlated with the enlargement and reshaping of the rostrum as males approached and attained sexual maturity.”

Wonder if those immature males were really just more primitive species with smaller size and smaller crest? Earlier Bennett erred by considering the morphological differences in various Pteranodon specimens ontogenetic, rather than phylogenetic. He failed to realize that Pteranodon specimens don’t get to giant size with giant crests without going through transitional mid-size specimens derived from certain small, crestless Germanodactylus specimens. The lamination of pterosaur skull bones is something first described here with the anterior extension of the jugal nearly to the tip of the rostrum. However, what these two workers are describing appears to be another thing entirely.

Martill and Moser 2017 wrote:
“Six specimens accessioned to the Bavarian State Collection for Palaeontology and Geology in Munich, Germany, in 1966 are identified as coming from a gigantic pterodactyloid pterosaur. The previously undescribed material was obtained in 1955 by Jean Otto Haas and compares favourably in size with the type specimen of the Late Cretaceous (Maastrichtian) azhdarchid pterosaur Arambourgiania philadelphiae (Arambourg 1959) from the same locality/region. The material represents fragments of two cervical vertebrae, a neural arch, a left femur, a ?radius, and a metacarpal IV and bones of problematic identity, and does not duplicate the type material of Arambourgiania. The timing of its collection and its locality of Ruseifa, Jordan suggest it might pertain to the same individual as the holotype.” 

Interesting. More parts for the same specimen? That’s like more pieces to the same puzzle. On the other hand, when the term ‘pterodactyloid’ pterosaur falls by the wayside, I will also celebrate. Azhdarchids are not closely related tp Pterodactylus.

Rigal et al. 2017 wrote:
“A specimen of a pterodactyloid pterosaur from the Upper Tunbridge Wells Sand Formation (Early Cretaceous, Valanginian) of Bexhill, East Sussex, southern England is described. It comprises a small fragment of jaw with teeth, a partial vertebral column and associated incomplete wing bones. The juxtaposition of the bones suggests that the specimen was originally more complete and articulated. Its precise phylogenetic relationships are uncertain but it represents an indeterminate lonchodectid with affinities to Lonchodectes sagittirostris (Owen 1874) which is reviewed here, and may belong in Lonchodraco Rodrigues & Kellner 2013. This specimen is only the third record of pterosaurs from this formation.”

England is famous for excellent preservation of pterosaur bits and pieces, mostly jaws, as is the case here. The specimen is named Serradraco and has been known for over 150 years.

Henderson 2017 wrote:
“Simple, three-dimensional, digital models of the crania and mandibles of 22 pterosaurs – 13 pterodactyloids and nine non-pterodactyloids (‘rhamphorhynchoids’) – were generated to investigate gross-level mechanical aspects of the skulls as they would related to feeding behaviour such as bite force and speed of jaw motions. The key parameter was the determination of second moments of area of the mid-muzzle region and the computation of the bending moment relative to the occiput. The shorter, stockier skulls of basal ‘rhamphorhynchoids’ were the strongest for their size in terms of potential resistance to dorso-ventral bending, and this finding correlates with their robust dentitions. More derived ‘rhamphorhynchoids’ showed the start of a trend towards weaker skulls, but faster jaw adduction was interpreted to be an adaptation for the snatching of small prey. Pterodactyloids continued the trend to lengthen the skull and to reduce its cross-sectional area, resulting in less stiff skulls, but more rapid opening and closing of the jaws. Changes in the rear of the skulls and the development of coronoid eminences on the mandibles of all the pterodactyloids are correlated with the reduction in bite force and a concomitant increase in jaw closing speed.”

This makes sense, though I worry that ‘simple digital models’ by Henderson have not fared well in the past.

Hone, Jiang and Xu 2017 wrote: 
“After being inaccessible for a number of years, the holotype and other specimens of the dsungaripterid pterodactyloid pterosaur Noripterus complicidens are again available for study. Numerous taxa assigned to the Dsungaripteridae have been described since the erection of Noripterus, but with limited comparisons to this genus. Based on the information from Young’s original material here we revise the taxonomic identity of N. complicidens and that of other Asian dsungaripterids. We conclude that N. complicidens is likely to be distinct from the material recovered from Mongolia and this latter material should be placed in a separate genus.”

Okay. Wonderful. Thought I think some of us knew that already based on photo data.

And speaking of southern England…
did the U. of Leicester clade ever find the grad student they advertised for to prove the pterosaur quad leap hypothesis?

References
2017. New Perspectives on Pterosaur Palaeobiology. Hone  DWE, Witton MP and Martill DM editors. Geological Society, London SP455.
Bennett SC and Penkalski P 2017. Waves of bone deposition on the rostrum of the pterosaur Pteranodon.
Dalla Vecchia FM 2017. A wing metacarpal from Italy and its implications for latest Cretaceous pterosaur diversity.
Henderson DM 2017. Using three-dimensional, digital models of pterosaur skulls for the investigation of their relative bite forces and feeding styles.
Hone DWE, Jiang S, and Xu X 2017. A taxonomic revision of Noripterus complicidens and Asian members of the Dsungaripteridae.
Martill DM and Moser M 2017. Topotype specimens probably attributable to the giant azhdarchid pterosaur Arambourgiania philadelphiae (Arambourg 1959).
Palmer C 2017. Inferring the properties of the pterosaur wing membrane.
Rigal S, Martill DM, and Sweetman SC 2017. A new pterosaur specimen from the Upper Tunbridge Wells Sand Formation (Cretaceous, Valanginian) of southern England and a review of Lonchodectes sagittirostris (Owen 1874).
Witton MP 2017. Pterosaurs in Mesozoic food webs: a review of fossil evidence.



Source: https://pterosaurheresies.wordpress.com/2017/03/20/new-perspectives-on-pterosaur-palaeobiology-volume/

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