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New monitor lizard fossils from China support Asian origin of monitor lizards

Figure 1 Reconstruction of Archaeovaranuslii. Credit: IVPP

Studies based on new monitor lizard fossil species from China show that the transition from ancient monitor lizards to monitor lizards took place in Asia, supporting the Asian origin of the monitor lizard family.


The study was published in Royal Society Philosophical Transactions B This was done by researchers at the Institute of Vertebrate Paleobiatology (IVPP) of the Chinese Academy of Sciences and collaborators in the United Kingdom and Switzerland.

The Lizardaceae, whose Chinese name literally means giant lizard, is one of the most successful groups of lizards. Its only extant genus, Varanas, covers more than 80 living species currently distributed in Africa, Asia and Australia, as well as some closely related fossils.

The lizard family is derived from the Late Cretaceous of Eurasia, and it is generally accepted that well-preserved fossils have been reported from the Late Cretaceous of the Gobi Desert in Mongolia and China.

However, the origin of the genus Varanas has been heavily controversial, with hypotheses proposed for Asia, Africa, and Gondwana. The earliest and definitive Fossil of Varanas comes from the early Neogene.

The Paleogene, which connects the Late Cretaceous and the Neogene, is an important period of the transition from monitor lizards to monitor lizards. However, the only fossils well represented during this important period are the North American Saniwa skeletons, which currently do not have Baranus, which further obscures the evolutionary history of the monitor lizards.

New monitor lizard fossils from China support Asian origin of monitor lizards

Figure 2 Holotype of Archaeovaranuslii from the Eocene of the Liguanqiao basin. Credit: IVPP

Archaeovaranuslii, a new fossil balanide from China, was unearthed in 2008 by a research group led by Professor Wang Yuanqing of IVPP from the Lower Eocene of the Liguanqiao Basin in Hubei Province.

Archaeovaranus was about 1 meter long. It shares many features with Baranus, such as an elongated nose, mandibular joints, and anterior condyle stenosis, but also with a low degree of fenestration of the open olfactory canal and orbit, palatal teeth, and coracoid process. It’s different from Baranus.

The most distinctive feature of Archaeovaranus is the similar length of the forelimbs and hindlimbs (manus and pes are not included). In contrast, the hind limbs of Baranus are clearly longer than the forelimbs.

New monitor lizard fossils from China support Asian origin of monitor lizards

Figure 3 Monitor lizard phylogeny (a) and monitor lizard fossil geographic location (b): Archaeovaranuslii is the closest relative of the monitor lizard. Credit: IVPP

Such proportions suggest that Archaeovaranus has adopted a special movement that is different from Saniwa in North America at least at the same time.Archaeovaranus individual represented by fossil He became sexually mature at the age of 5 and died at the age of 16.

Archaeovaranus also emphasizes the evolution of some feeding-related characters in the monitor lizard family. From stalk monitor lizards to monitor lizards, opening the orbit increased feeding efficiency, and closing the entorhinal tube was able to neutralize the increased stress caused by opening the orbit. On the other hand, the retention of the palatal teeth of Archaeovaranus suggests a complex history of tongue function from the migration of other lizard prey to the chemical sensation of Varanus.


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For more information:
Liping Dong et al, a new stem from the early Eocene of China-monitor lizard (reptile, scaled reptile), Royal Society Philosophical Transactions B: Biological Sciences (2022). DOI: 10.1098 / rstb.2021.0041

Quote: The new monitor lizard from China supports the Asian origin of the monitor lizard family (February 16, 2022).

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New monitor lizard fossils from China support Asian origin of monitor lizards

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