Phillolepids ( lat. Phyllolepida ) is a suborder of the placoderm from the order Arthrodiriformes [1] , who lived in the Middle and Upper Devonian [2] .
| † Phillolepids | |||||||||||||||||||||||||||||||||||||||||
 Phyllolepis orvini | |||||||||||||||||||||||||||||||||||||||||
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| International scientific name | |||||||||||||||||||||||||||||||||||||||||
Phyllolepida Stensiö , 1934 | |||||||||||||||||||||||||||||||||||||||||
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| Geochronology 416—359 Ma
◄ Nowadays◄ Cretaceous-Paleogene extinction◄ Triassic extinction◄ Mass Permian Extinction◄ Devonian extinction◄ Ordovician-Silurian extinction◄ Cambrian explosion | |||||||||||||||||||||||||||||||||||||||||
Content
Title
The name of the suborder is derived from the name of its type genus (phillolepis); the latter was described back in 1844 by J. L. R. Agassis from finds dating back to the Famennian age of the Upper Devonian. However, initially this genus was attributed to the jawless . Only in 1934, E. Stensho proved his affiliation with the placoderms, having identified the Phyllolepida detachment (at that time - monotypic ) in their composition. In the 1980s, other genera related to this taxon were discovered.
Description
The fossil remains of phyllopleids are found in freshwater sediments (on almost all continents). The size of these fish is quite large (the largest representatives reached 1.5 m in length). They had a flattened shape and possessed (like arthrodirs and antiarchs ) an extensive integumentary cuirass, which consisted of solid plates coated from above with a cosmic (modified dentin ). The shell plates have a characteristic relief of concentric ridges; they quite resemble (especially the presence of the posterior abdominal-lateral element) shell plate of typical arthrodirs, but differ in that the pectoral openings for the pectoral fins are not closed behind. The proportions of the plates vary greatly, and the medial plates are always much larger than the edge ones. The long and strong tail was not covered with shell, and the animal’s head was protected by one central plate; while the head-chest joint was formed by simple ends of the plates [3] .
Cartilage endocrine, the roof of the skull is flat. In the eye orbits - anterolateral position. The orifice is wide [2] .
The pectoral fins phyllopleid are wide and small, the ventral fins are elongated. The dorsal fin is always alone. The caudal fin is a long, difitsercal [4] .
Phillolepids were benthic predators; they probably waited for their prey, buried in the muddy bottom of the river, and then captured it with their open mouth, delivering sharp blows to their long tail. Since the orbits of the phyllopleids were extremely small, they are considered blind; rudimentary eyes were located on the sides of the head (while for sighted near-bottom predators such as flounder or stargazer , eye movement on the upper side of the head is typical). The phyllopleids were supposedly found their prey using sensory organs located in the grooves of the relief of the shell plates [5] .
Systematics
Paleontologists have different points of view on the position of phyllopleids in the placoderm class. In the 1970s, most scholars believed that the phylolepid sister group was the group consisting of arthrodir and antiarch [6] . In 1984, D. Gouger put forward arguments in favor of a different view on the phylogeny of the placoderm, according to which the phyllopleids are a sister group for arthrodirs, and both clades are far enough away from the antiarchs [7] ; subsequently, this view became widespread and is supported by the cladogram , built in the work of R. Carr, Z. Johanson and A. Ritchie in 2009 [8] .
The development of the latest version is the point of view reflected in the study of W. Dupree, Zhu Min and Wang Junqing in 2009. According to her, phyllopeids are actually very specialized arthrodirs and are part of the basal group of this largest placoderm squad [9] . In 2011, in his fundamental work on fish used precisely this point of view, giving the taxon phylloidid rank of suborder [1] .
Classification
Currently, the phyllopleid order is divided into two families:
- Gavinaspididae is a more primitive family containing the only genus from the Lower Devonian of China;
- Phyllolepididae is a more advanced family containing 6 genera: Cobandrahlepis , Yurammia , Cowralepis , Placolepis , and (among them, Placolepis has cosmopolitan distribution, Phyllolepis is represented in North America, fossils and fossils in Europe, relate to the early and middle Devonian of Australia).
Previously, the phyllepid order also included [10] the Antarctaspididae family with the genus Antarctaspis ; Now this family is attributed directly to the arthrodir detachment [11] .
Notes
- ↑ 1 2 Long JA The Rise of Fishes: 500 Million Years of Evolution. - Second Edition. - Johns Hopkins University Press. - 304 p. - ISBN 978-0-801-89695-8 .
- ↑ 1 2 Cherepanov, Ivanov, 2007 , p. 87.
- ↑ Carroll, vol. 1, 1992 , p. 68.
- ↑ Cherepanov, Ivanov, 2007 , p. 88.
- ↑ Nelson, 2009 .
- ↑ Denison, 1978 .
- ↑ Goujet D. F. Placoderm interrelationships: a new interpretation, with a short review of placoderm classifications // Proceedings of the Linnean Society of New South Wales. - 1984. - Vol. 107. - P. 211-243.
- ↑ Carr R. K., Johanson Z., Ritchie A. The phyllolepid placoderm Cowralepis mclachlani : Insights into the evolution of feeding mechanisms in jawed vertebrates // Journal of Morphology. - 2009. - Vol. 270, no. 7. - P. 775-804.
- ↑ Dupret V., Zhu Min, Wang Jun-Qing. The morphology of Yujiangolepis liujingensis (Placodermi, Arthrodira) from the Pragian of Guangxi (south China) and its phylogenetic significance // Zoological Journal of the Linnean Society. - 2009. - Vol. 157, no. 1. - P. 70-82.
- ↑ Carroll, vol. 3, 1993 , p. 172.
- ↑ Stillwell J. D., Long J. A. Frozen in Time: Prehistoric Life in Antarctica . - Victoria: CSIRO Publishing, 2011 .-- 248 p. - ISBN 978-0-643-09635-6 . - P. 71.
Literature
- Carroll R. Paleontology and evolution of vertebrates: In 3 volumes T. 1. - M .: Mir, 1992. - 280 p. - ISBN 5-03-001819-0 .
- Carroll R. Paleontology and the evolution of vertebrates: In 3 volumes T. 3. - M .: Mir, 1993. - 312 p. - ISBN 5-03-001819-0 .
- Nelson, J. S. Fish of the World Fauna / Transl. 4th English ed. Bogutskoy N.G., scientific. eds. Nasek A. M., Gerd A. S. - M .: Book House "LIBROKOM", 2009. - 880 p. - ISBN 978-5-397-00675-0 .
- Cherepanov G.O., Ivanov A.O. Paleozoology of vertebrates. - M .: Publ. Center "Academy", 2007. - 352 p. - ISBN 978-5-7695-3104-0 .
- Denison R. Placodermi. Handbook of Paleoichthyology, vol. 2. - Stuttgart, New York: Gustav Fischer Verlag, 1978.- 128 p. - ISBN 978-0-89574-027-4 .