Alienacanthus

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Alienacanthus
Temporal range:
Famennian, 371.1–358.9 Ma
A. malkowskii and Hadrosteus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: †Placodermi
Order: †Arthrodira
Suborder: †Brachythoraci
Family: †Selenosteidae
Genus: †Alienacanthus
Kulczycki, 1957
Type species
†Alienacanthus malkowskii
Julian Kulczycki, 1957

Alienacanthus (IPA: [ˌalienaˈkantʰus]) (meaning "Alien spine") is a genus of selenosteid placoderm from the Famennian Ostrówka Quarry in the Świętokrzyskie Mountains, Poland, and Kowala Quarry along with the Maïder Basin in the Anti-Atlas, Morocco. The type and only species is A. malkowskii, known from a handful of specimens.[1]

Description

Alienacanthus' holotype, MZ VIII Vp-45, was referred to A. malkowskii in 1957 by Kulczycki, (1957). It consists of what were originally interpreted as "fragments of large osseous spines".[1] However two epitypes described by Jobbins et al., (2024) that preserve more material shows that what Kulczycki, (1957) interpreted as "spines" are in fact fragmentary inferognathals.[2] The epitypes, PIMUZ A/I 5239 and MCD 201, both comprise "a nearly complete articulated skull with all gnathal elements." and "left side of partially preserved skull with all gnathal elements." respectively.[2] The combination of a short upper jaw and elongated lower jaw is a striking case of convergent evolution with halfbeaks.[2] Alienacanthus was likely piscivorous, with jaws bearing sharp, posteriorly recurved teeth on both its upper and lower jaws, suggesting a grasping and trapping live prey.

Etymology

The generic name, Alienacanthus (IPA: [ˌalienaˈkantʰus]), derives from the Latin 'aliena' which means alien, and 'canthus' which means spine, referring to what Kulczycki, (1957) thought were spines. The specific name, malkowskii (IPA: [ˌmawˈkɔvskiaɪ]), is named after Prof. St. Malkowski, the former Director of the Muzeum Ziemi in Warsaw; Poland.[1]

Classification

Originally, Kulczycki, (1957) described Alienacanthus as a putative placoderm, noting that the traits the holotype possessed did not belong in either Selachii or Acanthodii.[1] Jobbins et al., (2024) ran a parsimony analysis utilising a character matrix based on 98 characters for 28 taxa. The analysis resulted in Alienacanthus being recovered in Selenosteidae in a polytomy with Amazichthys, and a polytomic clade comprising Melanosteus, Enseosteus, Walterosteus, and Draconichthys.[2] Their results are shown below:

Arthrodira

References

  1. ^ a b c d Kulczycki, Julian (1957). "UPPER DEVONIAN FISHES FROM THE HOLY CROSS MOUNTAINS (POLAND)". Acta Palaeontologica Polonica. 2 (4): 285–380. Retrieved 31 January 2024.
  2. ^ a b c d Jobbins, Melina; Martin Rücklin, Martin; Sánchez Villagra, Marcelo R.; Lelièvre, Hervé; Grogan, Eileen; Szrek, Piotr; Klug, Christian (31 January 2024). "Extreme lower jaw elongation in a placoderm reflects high disparity and modularity in early vertebrate evolution". Royal Society Open Science. 11. doi:10.1098/rsos.231747. PMID 38298398. S2CID 267331593. Retrieved 31 January 2024.
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