Gondwanaspis, Feist, 2002

Feist, Raimund, 2002, Trilobites from the latest Frasnian Kellwasser Crisis in North Africa (Mrirt, central Moroccan Meseta), Acta Palaeontologica Polonica 47 (2), pp. 203-210 : 204-205

Genus Gondwanaspis gen. nov.

Derivation of name: Gondwana, after the paleogeographic occurrence of the new taxon; aspis, heavily armed (with spines).

Type species: Gondwanaspis mrirtensis sp. nov.

Assigned species: G. mrirtensis sp. nov.,? Ceratocephala (Leonaspis) harborti Richter and Richter, 1926 .

Diagnosis.—Cephalon with glabellar lobes not inflated, rectangular central lobe; straight ocular ridges; no sutural ridges; eye shifted in midst of genal field; no occipital spines; straight, outward directed librigenal spine, exceeding length of glabella; spines along the entire anterior and antero−lateral margins.

Remarks.— Gondwanaspis gen. nov. from the latest Frasnian beds immediately preceding the Upper Kellwasser level both at Mrirt and Coumiac (Montagne Noire), is the youngest known representative of the Odontopleuridae . Together with a new and so far undescribed species from the McWhae Ridge area, Canning Basin, Western Australia, its occurrence seems to be restricted to terrains of the Gondwana margin. The poorly known mid−Frasnian Ceratocephala (Leonaspis) harborti Richter and Richter, 1926 , that was assigned by Bruton (1968) to the Silurian genus Dudleyaspis , shares with the new genus the rectangular central glabellar lobe and the absence of sutural ridges. However, it is distinct in its swollen lateral glabellar lobes where the anterior third pair is well represented. The latter is inconspicuous or lacking in Gondwanaspis . It is not known whether C. (L.) harborti carries spines on the cranidial anterior border, which is an important feature of the new genus. After the discovery of complete material including pygidia, the possible inclusion of C. (L.) harborti in the new genus might be reconsidered, the diagnosis being emended to accommodate this inclusion.

Comparisons.—The new genus shares only a few traits with previously known late Devonian representatives of the Odontopleuridae , such as Leonaspis, Radiaspis , and Koneprusia , which exhibit back−curved ocular ridges and genal spines, as well as eyes positioned near to the posterior margin. In this regard and despite the considerable difference in age, it is more closely related to the Silurian Dudleyaspis Prantl and Přibyl, 1949 and in particular to D. uncifera from Gotland ( Ramsköld 1984). It differs from Dudleyaspis in having a rectangular central glabellar lobe, the lateral lobes not swollen, the anteriormost of which are inconspicuous, in absence of sutural ridges, in having straight border spines that are also present on the central portion of the anterior border, and in the considerably advanced, not back−curved genal spine. Dudleyaspis was included by Ramsköld and Chatterton (1991) in the subfamily Acidaspidinae Salter, 1864 . Though the origin of the new taxon is somewhat enigmatic, as no direct Devonian ancestors are known so far, it is tentatively assigned here to the Acidaspidinae , because of the close resemblance to Dudleyaspis . This attribution will need to be reconsidered after the discovery of the so far unknown thoracic and pygidial features.