Hamipterus

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Hamipterus
Temporal range: Early Cretaceous, 120 Ma
Hamipterus skull at the Paleozoological Museum of China.jpg
Skull on display at the Paleozoological Museum of China.
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Order: Pterosauria
Suborder: Pterodactyloidea
Clade: Pteranodontoidea
Genus: Hamipterus
Wang et al., 2014
Type species
Hamipterus tianshanensis
Wang et al., 2014

Hamipterus is an extinct genus of pteranodontoid pterosaur from the Early Cretaceous of northwestern China. It is known from a single species, the type species Hamipterus tianshanensis.[1]

Discovery and naming[edit]

In 2006 from the Hami region in Xinjiang, a Konservat-Lagerstätte was reported, in this case lake sediments allowing for an exceptional preservation of fossils. The same year, Qiu Zhanxiang and Wang Banyue started official excavations. Part of the finds consisted of dense concentrations of pterosaur bones, associated with soft tissues and eggs. It was concluded that the site represented a nesting colony that storm floods had covered with mud. Dozens of individuals could be secured from a total that in 2014 was estimated to run into the many hundreds.[1]

In 2014, the type species Hamipterus tianshanensis was named and described by Wang Xiaolin, Alexander Kellner, Jiang Shunxing, Wang Qiang, Ma Yingxia, Yahefujiang Paidoula, Cheng Xin, Taissa Rodrigues, Meng Xi, Zhang Jialiang, Li Ning and Zhou Zhonghe. The generic name combines that of the Hami region with a Latinised Greek πτερόν, pteron, "wing". The specific name refers to the provenance from the Tian Shan, a mountain range.[1]

The holotype, IVPP V18931.1, has been found in a layer of the Tugulu Group dating from the Lower Cretaceous. It consists of a skull, probably of a female. The paratype is IVPP V18935.1, the skull of a male individual. The inventory number IVPP V18931 does not pertain to a single skeleton but to a block containing various bones of different individuals. Eleven such blocks had in 2014 been secured, numbered IVPP V18931 to V18941. Together they comprise the remains of at least forty animals, both bones and soft tissue remnants such as the horn sheaths of skull crests. Exceptionally for pterosaur fossils, the bones have not been crushed but were preserved three-dimensionally in good condition. Five uncrushed eggs were also found. The finds in 2014 represented the largest known concentration of pterosaur fossils, with the exception of the Pterodaustro nesting colonies of Argentina.[1]

Description[edit]

The wingspan of the individuals described in 2014 ranged from 1.5–3.5 metres (4 ft 11 in–11 ft 6 in).[1]

The describing authors indicated some distinguishing traits, all of them autapomorphies, unique derived characters. The dentary, the front bone of the lower jaw, has a hook-shaped process. The ascending branch of the jugal bone, running to the lacrimal bone, is thin, inclined to the front and expanded at the top. The central supraoccipital of the top rear skull bears a well-developed crest. The humerus is perforated by a pneumatic foramen near the base of the deltopectoral crest. The outer lower carpal bone of the wrist has a spike-shaped process pointing to below.[1]

Also a unique combination is present of traits that in themselves are not unique. The front snout bone, the praemaxilla, bears a crest with ridges and grooves that curve to the front. The groove on the dentary reaches the highest point of that bone. Both the snout tip and the tip of the lower jaws are slightly expanded. The deltopectoral crest is moderately twisted around the longitudinal axis of the humerus.[1]

Phylogeny[edit]

Hamipterus was within the Pterodactyloidea, placed into the Pteranodontoidea. An exact cladistic analysis could not resolve the relationship with Istiodactylus, Ludodactylus and the Anhangueridae.[1]

Paleobiology[edit]

The large number of individual found allowed to establish a growth series, showing how individuals developed through their ontogeny. Larger animals feature a number of changes. Their snout tips become relatively wider. The snout crest becomes more robust and expands its base towards the front, beginning at the level of the fifth tooth instead of the sixth. The pattern of grooves and ridges on the crest grows more prominent. The snout tip also starts to straighten in side view, no longer curving upwards. The groove in the dentary deepens and lengthens as well. No change however, takes place in the number of teeth, the degree of fusion in the symphysis of the lower jaws or the shape of the postcranial skeleton, as far as this can be ascertained, given the fact that the elements behind the skull were not found articulated.[1]

It was assumed that a clear sexual dimorphism was discovered, the largest specimens sporting the largest crests being the males while smaller individuals were females with smaller crests. This was seen as a refutation of the hypothesis that with pterosaurs only the males possessed crests.[1]

See also[edit]

References[edit]

  1. ^ a b c d e f g h i j Xiaolin Wang; Alexander W.A. Kellner; Shunxing Jiang; Qiang Wang; Yingxia Ma; Yahefujiang Paidoula; Xin Cheng; Taissa Rodrigues; Xi Meng; Jialiang Zhang; Ning Li; Zhonghe Zhou (2014). "Sexually dimorphic tridimensionally preserved pterosaurs and their eggs from China". Current Biology. 24 (12): 1323–1330. doi:10.1016/j.cub.2014.04.054. PMID 24909325.
  • Xiaolin Wang, Alexander W. A. Kellner, Shunxing Jiang, Xin Cheng, Qiang Wang, Yingxia Ma, Yahefujiang Paidoula, Taissa Rodrigues, He Chen, Juliana M. Sayão, Ning Li, Jialiang Zhang, Renan A. M. Bantim, Xi Meng, Xinjun Zhang, Rui Qiu & Zhonghe Zhou (2017). Egg accumulation with 3D embryos provides insight into the life history of a pterosaur. Science 358(6367): 1197-1201. doi: 10.1126/science.aan2329