Asperocephalus milleri Ahlberg (nomen nudem)

A big tooth from Asperocephalus milleri.

This porolepiform fish, received its new name by Per Ahlberg in his 1989 unpublished thesis on Glyptolepis from Scotland (see references). It is one of the biggest fish in the lake and a fierce predator. The fish is very rare, as is often the case with predators at the top of the food chain. More work needs to be done on this species. This porolepiform can be compared with the genus Laccognathus from Latvia and Estonia and more recently from Canada, (Downs 2011).

In the collections of the NMS an almost complete head of this species is stored. On the ventral side some scales are visible (see one figured below). This head was first described by Thomson in 1966 as Glyptolepis paucidens. Typical for the scales of this species, is that they have only tubercles and no ridges running from the centre to the scale to the edge, like the scales of Glyptolepis. In the general part on porolepiforms, a thin section through a scale (see below) is shown.

Here we show a picture of such a scale. The dermal plates are also covered with tiny tubercles while the plates from Glyptolepis are smooth.

Scale of Aspherocephalus milleri.

Scale used to make thin sections, see histology and morphology part of Crossopterygians.(NMS G.2016.32.253 ©) .

Scale on back of big head described by Thompson 1966, NMS ©.

Incomplete lower jaw seen from the outside, figured by Hugh Miller in 1849, in ‘Footprints of the creator: the Asterolepis of Stromness.’ Hugh Miller found several plates of Homostius, scales of Glyptolepis and the lower jaw figured above and determined they all belonged to the genus Asterolepis. Asterolepis was known from the Old Red Sandstone from Russia and was described by Eichwald in 1840. Probably, Miller did not have access to the papers and books from eastern Europe and Russia. In his book the ‘Asterolepis of Stromness’ he describes three different species as belonging to Asterolepis, but the big dermal plates figured belong to Homostius milleri, the scales to Glyptolepis paucidens and the lower jaw figured (above and below) to Aspherocephalus milleri. See also on this site: page on placoderms, antiarchs and Asterolepis.

Incomplete lower jaw seen from the inside, figured by Hugh Miller in 1849. Miller also figured a lower jaw of Glyptolepis as a jaw of Asterolepis, see below (original drawing and text).

Lower jaw of Glyptolepis paucidens (after Miller 1849).

The lower Jaw figured by Hugh Miller in 1849 (collections NMS ©).

Medium sized lower jaw of Asperocephalus milleri in outside view, beautifully prepared by Jon Jeffery (see also his papers on the crossopterygian Rhizodus) (collection NMS ©).

Same jaw as above seen from the inside.

Close-up of above.

Very large lower jaw (collection NMS, ©).

Two lower jaws in position, (collection NMS, ©).

Parietal and post parietal plates seen on the outside, compared between Aspherocephalus milleri on the left and Glyptolepis paucidens on the right. P: parietal, PP: post parietal. (collection NMS ©).

Parietal and post parietal plates seen on the inside, compared between Aspherocephalus milleri on the left and Glyptolepis paucidens on the right. P: parietal, PP: post parietal. (collection NMS ©).

References:

  • Ahlberg, P.E., 1989, The anatomy and phylogeny of Porolepiform fishes, with special reference to Glyptolepis, Unpublished theses.
  • Ahlberg, P.E., 1992, The palaeoecology and evolutionary history of the porolepiform sarcopterygians, in: Fossil fishes as living animals Ed. Elga Mark-Kurik, Tallinn.
  • Downs, J.P. , Edward B. Daeschler , Farish A. Jenkins JR. & Neil H. Shubin, 2011, A new species of Laccognathus (Sarcopterygii,Porolepiformes) from the Late Devonian of Ellesmere Island, Nunavut, Canada, Journal of Vertebrate Paleontology 31(5):981–996,
  • Eichwald, E. 1840. Die Tier- und Pflanzenreste des alten roten Sandsteins und Bergkalks im Nowgorodschen Gouvernement. Saint-Petersburg Academy Imperial of Sciences, Bulletin of Sciences, 7:78-91.
  • Jeffery, J.E., 1998, The Morphology and Phylogeny of the European members of Order Rhizodontida (Pisces: Sarcopterygii), theses
  • Miller, H. 1849, Footprints of the creator: the Asterolepis of Stromness
  • Thomson, K.S. 1966, Glyptolepis from the Middle Devonian of Scotland. Postilla, No. 99, April 16, 3-11
  • Downs, J.P. , Edward B. Daeschler , Farish A. Jenkins JR. & Neil H. Shubin, 2011, A new species of Laccognathus (Sarcopterygii,Porolepiformes) from the Late Devonian of Ellesmere Island, Nunavut, Canada, Journal of Vertebrate Paleontology 31(5):981–996,

Porolepiform