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| Harajicadectes zhumini Choo, Holland, Clement, King, Challands, Young & Long, 2024 Illustration by Brian Choo |
ABSTRACT
Remote Devonian exposures in central Australia have produced significant but highly fragmentary remains of fish-grade tetrapodomorphs. We describe a new tetrapodomorph from the Middle–Late Devonian (Givetian–Frasnian) Harajica Sandstone Member of the Amadeus Basin, Northern Territory, which is represented by several nearly complete skulls along with much of the body and postcranial skeleton. The new form has a posteriorly broad postparietal shield, broad, triangular extratemporal bones, and a lanceolate parasphenoid. The spiracular openings are particularly large, a character also recorded in elpistostegalians and Gogonasus, demonstrating that these structures, suggestive of spiracular surface air-breathing, appeared independently in widely differing nodes of the stem-tetrapod radiation. A phylogenetic analysis resolves the new form within a cluster of osteolepidid-grade taxa, either as part of a polytomy or as the most basally-branching representative of a clade containing ‘osteolepidids,’ canowindrids, and megalichthyids.
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| Harajicadectes zhumini from the Harajica Sandstone Member (Givetian–Frasnian), Northern Territory, Australia, Holotype NTM P6410. A, photographed as a natural mold in situ as it was discovered in 2016; B, as a whitened latex peel; and C, interpretative drawing. |
SYSTEMATIC PALEONTOLOGY
OSTEICHTHYES Huxley, 1880
SARCOPTERYGII Romer, 1955
TETRAPODOMORPHA Ahlberg, 1991
Genus HARAJICADECTES gen. nov.
HARAJICADECTES ZHUMINI, gen. nov. et sp. nov.
Diagnosis—Tetrapodomorph fish with greatly enlarged spiracular openings, comprising over 20% of the total length of the skull-roof, bordered by the tabular, extratemporal, and squamosal. Parietal and postparietals of roughly equal length. Elongate intertemporal that widens anteriorly. Posterior nasals narrower than the anterior and posterior supraorbitals. Median extrascapular tapers anteriorly into a V-shaped recess formed by the large rounded lateral extrascapulars. Elongate lanceolate parasphenoid with denticles larger on the anterior part of the bone. Scales display ridged ornamentation and lack cosmine. Anterior squamation cycloid, abruptly shifting to a rhombic shape on the rear flank.
Etymology—“Harajica Biter.” Named for the Harajica Sandstone Member and the ancient Greek dēktēs (“biter”) in reference to the animal’s large fangs and presumed predatory habits. The species honors Professor Min Zhu of the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China, for his numerous contributions to early vertebrate paleontology.
Type Locality and Horizon—Harajica Sandstone Member of the Parke Siltstone. Locality 6 of Young (Citation1985), about 2 km southwest of the southern end of Stokes Pass, Amadeus Basin, Northern Territory. Givetian–Frasnian in age (Fig. 1).
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| Life reconstruction of Harajicadectes zhumini, a 40 cm long lobe-finned fish that is not too distantly related to the fishes that gave rise to the earliest limbed tetrapods. (Illustration by Brian Choo, Flinders University) |
Brian Choo, Timothy Holland, Alice M. Clement, Benedict King, Tom Challands, Gavin Young and John A. Long. 2024. A New Stem-Tetrapod Fish from the Middle–Late Devonian of central Australia. Journal of Vertebrate Paleontology. e2285000. DOI: 10.1080/02724634.2023.2285000