Proterocidaridae Smith, 1984

Hausmann, Imelda M., Nützel, Alexander, Roden, Vanessa Julie & Reich, Mike, 2021, Palaeoecology of tropical marine invertebrate assemblages from the Late Triassic of Misurina, Dolomites, Italy, Acta Palaeontologica Polonica 66 (1), pp. 143-192 : 177-178

Family Proterocidaridae Smith, 1984 Genus Pronechinus Kier, 1965

Type species: Pronechinus anatoliensis Kier, 1965 ; Turkey, Permian.

Pronechinus ? sp. Fig. 30G, J, L, M .

?2014 Unknown echinoderm plate; Nützel and Kaim 2014: fig. 11p, q.?2017 Dissociated ambulacral test plate of a proterocidaroid, with peripodial rim indicated; Thuy et al. 2017a: fig. 1B.

Material.—Total more than 60 ambulacral and interambulacral plates (including PZO 12777–12780) from Misurina Landslide bulk samples, Italy, Carnian, Triassic.

Description.—This species is known only from disarticulated plates. One type of ambulacral plates oblongate polygonal in shape, with a marginal pore pair (without distinct peripodial rim) and an imperforate primary tubercle accompanied by a minute secondary tubercle ( Fig. 30G ). Another, and more common second type of ambulacral plates almost subcircular to circular in shape, with a central pore pair surrounded by a slightly distinct peripodial rim, and also bearing adjacent smaller secondary tubercles ( Fig. 30J, L, M ). Interambulacral plates rectangular to polygonal in shape, with up to 10 minute secondary tubercles.

Remarks.—This putative proterocidarid material is remarkable because it provides evidence for persistence of this

Palaeozoic” echinoid stem group for at least 16 Ma after the Permian/Triassic boundary. Misurina Landslide is the same locality from which a representative of another

Palaeozoic-type” echinoderm group, the Ophiocistioidea, was recently described ( Reich et al. 2018). These findings are in accordance with other Triassic stem group echinoids recently reported from France ( Hagdorn 2018), China ( Thuy et al. 2017a; Thompson et al. 2018), and potentially Italy (Thompson et al. 2019).

Figures

Fig. 30. Echinoderm plates, ossicles, and elements from Misurina Landslide, northern Italy, Cassian Formation; Carnian, Upper Triassic. A. PZO 12765, isocrinid? (sediment encrusted) columnal. B. PZO 12878, asteroid?/asterozoan spine. C, D, H. Ophiuroids. C. PZO 12879, lateral arm plate, external view, showing the articulation for the attachment of spines.D. PZO 12880, arm vertebra, distal view, showing the muscle attachment area. E. PZO 12885, part of ambulacrum of unknown cidaroid? species. H. PZO 12881, distal lateral arm plate, in external view. F. PZO 11827, ophiocistioid goniodont Linguaserra triassica Reich in Reich et al., 2018, abaxial face, in outer view. G. Pronechinus? sp., PZO 12777, ambulacral plate. I. PZO 12884, broken hollow cidaroid? spine fragment, showing the microstructure at the inner side of the cylinder.J, L, M.Ambulacral plates of Pronechinus? sp. with slightly developed peripodial rim surrounding pore pairs (J, PZO 12780; L, PZO 12778; M, PZO 12779). K, N. Cidaroid? spines (partially broken) of unknown species (K, PZO 12882; N, PZO 12883).