Amazichthys, Holonema, Dickosteus, Incisoscutum and Dunkleosteus

Amazichthys trinajsticae (Jobbins et al 2022; Late Devonian) was preserved with a body outline indicating a deep caudal and dorsal fin. Otherwise this placoderm was a larger Millerosteus in most respects, but with a shorter thorax shield – and small sharp teeth! The cheek bones remain unknown and are restored here based on Millerosteus.

Holonema westolli (Claypole 1883, Miles 1971, Trinajstic 1999, Late Devonian) is a basal arthrodire. Note the primitive jaws without marginal teeth and small orbits.

Eastmanosteus calliapsis (Obruchev 1963, originally Dinichthys pustulosus Eastman 1907; Middle Devonian; skull length 27cm, est body length 1.5m)

Dunkleosteus terrelli (originally Dinichthys terrelli Newberry 1873; Late Devonian; up to 6m in length) is one of ten species representing the largest placoderms. Free-swimming and ferocious, Dunkleosteus was the apex predator of its time. Distinct from flatter placoderms, this taxon had a taller skull and deeper jaws. Sharpened bone took the place of teeth.

Presently, and subject to change with taxon addition, this taxon nests as one of the most basal placoderms, derived from Squatina, the angel shark.

Tetrapod skull bone identities have been applied to this taxon.

Ahlberg P, Trinajstic K, Johanson Z and Long J 2009. Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires. Nature. 460: 888–889.

Claypole EW 1883. Note on a large fish plate from the Upper Chemung? of northern Pennsylvania. Proceedings of the American Philosophical Society 20:664–667.

Eastman CR 1907. NY State Museum Memoir 10: 130.

Hu Y, Lu J and Young GC 2017. New findings in a 400 million-year-old Devonian placoderm shed light on jaw structure and function in basal gnathostomes. Nature Scientific Reports 7: 7813 DOI:10.1038/s41598-017-07674-y

Jobbins M, Rücklin M, Ferrón HG and Klug C 2022. A new selenosteid placoderm from the Late Devonian of the eastern Anti-Atlas (Morocco) with preserved body outline and its ecomorphology. Frontiers in Ecology and Evolution 10:969158.
doi: 10.3389/fevo.2022.969158

Lehman JP 1956. Les arthrodires du Dévonien supérieur du Tafilalet (sud marocain). Notes et Mémoires. Service Géologique du Maroc 129: 1–170.

Long J 1992. A new ploudosteid arthrodire from the Upper Devonian Gogo Formation of Western Australia. Palaeontology. 38: 39–62.

Long JA 1995. The Rise of Fishes. Johns Hopkins University Press. Baltimore and London.

Newberry JS 1873. Descriptions of fossil fishes. Report of the Geological Survey of Ohio 1(2): 245–355.

Obruchev DV 1964. Class Placodermi: pp 168–259 in Fundamentals of Paleontology. Volume 11. Agnatha. Pisces. Obruchev DV (ed) Israel Program for Scientific Translations. Jerusalem.

Stensiö EA 1959. On the pectoral fin and shoulder girdle of the arthrodires. K. svenska VetenskAkad. Handl. (9):2.

Trinajstic K 1999. New anatomical information on Holonema (Placodermi) based on material from the Frasnian Gogo Formation and the Givetian-Frasnian Gneudna Formation, Western Australi. Geodiversitas 21(1):69–84.

Woodward AS 1891. Catalogue of the Fossil Fishes in the British Museum (Natural History). Part II. Catalogue of the Fossil Fishes in the British Museum (Natural History) 2.

Young GC, Lelièvre H and Goujet D 2001. Primitive jaw structure in an articulated brachythoracid arthrodire (placoderm fish; Early Devonian) from southeastern Australia. J. Vertebr. Paleontol. 21: 670–678.

wiki/Dunkleosteus
wiki/Eastmanosteus
wiki/Arthrodira
wiki/Placodermi
wiki/Holonema
wiki/Amazichthys