For over 70 million years, during the Paleozoic, the placoderms (Greek for 'plated skin'), an extinct group of armoured fishes, were the most abundant and diverse vertebrates on our planet. Some of the first placoderm fossils discovered - such as Bothriolepis with its bone-covered pectoral fins - seemed so bizarre that they were thought to represent turtles or ancient beetles. All placoderms bear thick overlapping dermal plates around the head (called the 'head shield') and an area of the body covered in similar overlapping plates enveloping the pectoral to anal region (called the 'trunk-shield'). Placoderm fossils (Figure 1) are known from every continent on Earth ranging from the early Silurian (∼438 million years ago) to the end Devonian (∼359 million years ago) when they became extinct.
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http://dx.doi.org/10.1016/j.cub.2023.11.038 | DOI Listing |
PeerJ
December 2024
College of Science and Engineering, Flinders University of South Australia, Adelaide, Australia.
Well-preserved specimens of a new species of arthrodiran placoderm, sp. nov. (Middle Devonian of Victoria, Australia), reveals previously unknown information on the dermal skeleton, body-shape and dentition of the wide-spread genus .
View Article and Find Full Text PDFR Soc Open Sci
January 2024
Department of Palaeontology, University of Zurich, Karl-Schmid-Strasse 4, 8004 Zurich, Switzerland.
Jaws are a key vertebrate feature that arose early in our evolution. Placoderms are among the first jawed vertebrates; their fossils yield essential knowledge about the early diversification of gnathostome feeding strategies, diets and modularity. Modularity can be expressed through disproportional lengths of lower and upper jaws as in swordfish or halfbeaks.
View Article and Find Full Text PDFCurr Biol
January 2024
School of Molecular and Life Sciences, Curtin University, Bentley, WA 6076, Australia.
For over 70 million years, during the Paleozoic, the placoderms (Greek for 'plated skin'), an extinct group of armoured fishes, were the most abundant and diverse vertebrates on our planet. Some of the first placoderm fossils discovered - such as Bothriolepis with its bone-covered pectoral fins - seemed so bizarre that they were thought to represent turtles or ancient beetles. All placoderms bear thick overlapping dermal plates around the head (called the 'head shield') and an area of the body covered in similar overlapping plates enveloping the pectoral to anal region (called the 'trunk-shield').
View Article and Find Full Text PDFNat Commun
November 2023
CAS Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044, Beijing, China.
Major groups of jawed vertebrates exhibit contrasting conditions of dermal plates and scales. But the transition between these conditions remains unclear due to rare information on taxa occupying key phylogenetic positions. The 425-million-year-old fish Entelognathus combines an unusual mosaic of characters typically associated with jawed stem gnathostomes or crown gnathostomes.
View Article and Find Full Text PDFNature
November 2023
The Natural History Museum, London, UK.
The origin of vertebrate paired appendages is one of the most investigated and debated examples of evolutionary novelty. Paired appendages are widely considered as key innovations that enabled new opportunities for controlled swimming and gill ventilation and were prerequisites for the eventual transition from water to land. The past 150 years of debate has been shaped by two contentious theories: the ventrolateral fin-fold hypothesis and the archipterygium hypothesis.
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