Temporal range:
Reconstruction of Palaeospondylus as an agnathan
Scientific classification

Traquair, 1890
P. gunni
Binomial name
Palaeospondylus gunni
Traquair, 1890

Palaeospondylus is a fish-like fossil vertebrate. Its fossils are described from the Achanarras slate quarry in Caithness, Scotland.

The fossil as preserved is carbonized, and indicates an eel-shaped animal up to 6 centimetres (2 in) in length. The skull, which must have consisted of hardened cartilage, exhibits pairs of nasal and auditory capsules, with a gill apparatus below its hinder part, and ambiguous indications of ordinary jaws.[citation needed]

The phylogeny of this fossil has puzzled scientists since its discovery in 1890, and many taxonomies have been suggested. In 2004, researchers proposed that Palaeospondylus was a larval lungfish.[1] Previously, it had been classified as a larval tetrapod, unarmored placoderm, an agnathan, an early stem hagfish, and a chimera.[2][3] A 2017 study suggested that it was a stem chondrichthyan.[4]

In 2022, researchers report, based on studies using synchrotron radiation X-ray micro-computed tomography, that the neurocranium of Palaeospondylus was similar to those of the stem-tetrapods Eusthenopteron and Panderichthys, and concluded that Palaeospondylus was between those two phylogenetically.[5]

  1. ^ Thomson, K.S. (2004). "A Palaeontological Puzzle Solved?". American Scientist. 92 (3): 209–211. doi:10.1511/2004.47.3425. JSTOR 27858385.
  2. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 33. ISBN 1-84028-152-9.
  3. ^ Hirasawa, T; Oisi, Y; Kuratani, S (2016). "Palaeospondylus as a primitive hagfish". Zoological Letters. 2 (1): 20. doi:10.1186/s40851-016-0057-0. PMC 5015246. PMID 27610240.
  4. ^ Johanson, Zerina; Smith, Moya; Sanchez, Sophie; Senden, Tim; Trinajstic, Kate; Pfaff, Cathrin (2017). "Questioning hagfish affinities of the enigmatic Devonian vertebrate Palaeospondylus". Royal Society Open Science. 4 (7): 170214. Bibcode:2017RSOS....470214J. doi:10.1098/rsos.170214. PMC 5541543. PMID 28791148.
  5. ^ Hirasawa, Tatsuya; et al. (25 May 2022). "Morphology of Palaeospondylus shows affinity to tetrapod ancestors". Nature. 50. doi:10.1038/s41586-022-04781-3. Retrieved 25 May 2022.

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