Diacanthaspis Whittington 1941

Diacanthaspis Whittington, 1941 Type species. Diacanthaspis cooperi Whittington, 1941, Martinsburg Formation (lower Katian), Virginia, USA (Laurentia). Other species. The format of this list is similar to that used by Ramsköld and Chatterton (1991, pp. 364– 368) and Adrain and Chatterton (1994, p. 311), with the exceptions that sclerite types, mode of preservation, and palaeocontinent or terrane are also reported (the latter largely following the terminology of Torsvik and Cocks [2017]). Order of information is: specific epithet and authorship; original genus attribution; provenance, age, and paleogeographic occurrence; sclerite types known; preservation. conica Hammann, 1992; Diacanthaspis (Diacanthaspis); Cystoid Limestone Formation (upper Katian), Zaragoza Province, Spain (Iberian Gondwana); cranidia, librigenae, partial thorax, pygidia; internal molds and latex casts from external molds. decacantha Angelin, 1854; Cyrtometopus?; Jonstorp Formation (upper Katian), Västergötland, Sweden (Baltica); dorsal exoskeleton with poorly preserved cephalon, rear portion of thoracopygidium; calcareous; Kielan (1960) referred material (latex casts from external molds) with good preservation of the cephalon from the Holy Cross Mountains, Poland, but the state of preservation of the Swedish types limits confidence in the assignment. The Swedish type material was also revised by Bruton (1966a, p. 11, pl. 2, figs 7, 8). divaricata Whittard, 1961; Diacanthaspis; Spy Wood Sandstone Formation (Sandbian), Shropshire, England (Eastern Avalonia); one incomplete cranidium; internal mold. elapsa Tripp, 1954; Diacanthaspis; Craighead Formation (lower Katian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); cranidia, librigena, pygidia; internal molds. grayae Etheridge, 1878; Acidaspis; Balclatchie Formation (Sandbian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); dorsal exoskeleton, librigena, partial thoracopygidia, thoracic se g ments, pygidia; internal molds. Has been considered a junior subjective synonym of lalage; see comments under that entry. hollandi Chatterton and Perry, 1983; Diacanthaspis (Diacanthaspis); Delorme Formation (Sheinwoodian), Northwest Territories, Canada (Laurentia); cranidia, librigenae, hypostomes, thoracic segments, pygidia; silicified. hystrix Thomson, 1857; Acidaspis; Balclatchie Formation (Sandbian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); dorsal exoskeletons, cranidium, librigena, thoracopygidium, pygidium; internal molds. While it might seem from the list of sclerite types that this is a well known species, almost all of the available illustrations are very old drawings (Thomson, 1857, pl. 6, figs 6, 9, 10 [only]; Nicholson and Etheridge, 1878, pl. 8, figs 23–25; Reed, 1906, pl. 16, figs 3–5). The only photograph ever published is Tripp’s (1980a, pl. 4, fig. 31) tiny illustration of a ventral view of a single librigena. krizi Mergl, 2014; Diacanthaspis (Diacanthaspis); Králův Dvůr Formation (upper Katian), Prague Region, Czechia (Perunica); cranidia, librigenae, pygidia; internal and external molds. lalage Thomson, 1857; Acidaspis; Balclatchie Formation (Sandbian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); cranidia, thoracic segments, partial thoracopygidium; internal molds. As with hystrix, most of the available illustrations are early drawings (Thomson, 1857, pl. 6, figs 1–5; Nicholson and Etheridge, 1878, pl. 8, figs 17, 18, 20–22; Reed, 1906, pl. 16, fig. 6). The only photograph ever published is Tripp’s (1980a, fig. 30) oblique view of a hypostome. Reed (1906, p. 115) expressed doubt as to whether A. lalage and A. grayae were truly distinct. Tripp (1980a, p. 134) synonymized them. Acidaspis grayae has never been photographically illustrated and the most recent published drawings are those of Reed (1906). Until both species are revised with modern photographic illustrations of the available specimens, their potential synonymy is impossible to assess. lepidus Whittington, 1956; Diacanthaspis; Edinburg Formation (Sandbian), Virginia, USA (Laurentia); cranidia, librigena, hypostome, thoracic segment, partial thoracopygidium, pygidia, protaspid; silicified. maquoketensis Walter, 1924; Ceratocephala; Maquoketa Formation (lower Katian), Iowa, USA (Laurentia); dorsal exoskeleton lacking pygidium; latex cast from external mold. Revised herein. margaritata Hammann, 1992; Diacanthaspis (Diacanthaspis); Cystoid Limestone Formation (upper Katian), Zaragoza Province, Spain (Iberian Gondwanaland); cranidia, librigenae, pygidia; internal molds and latex casts from external molds. morenica Hammann, 1976; Diacanthaspis; Bancos Mixtos Formation (lower Katian), Ciudad Real Province, Spain (Iberian Gondwanaland); dorsal exoskeletons, cranidia; internal molds and latex casts from external molds. orandensis Whittington, 1956; Diacanthaspis; Oranda Formation (Sandbian), Virginia, USA (Laurentia); cranidia, librigenae, hypostomes, thoracic segments, pygidia; silicified. parvula Walcott, 1877; Acidaspis; Rust Formation (lower Katian), New York, USA (Laurentia); dorsal exoskeletons; calcareous. The only photograph ever published is Brett et al.’s (1999, fig. 9.8) illustration of a paratype. playfairi Reed, 1914; Acidaspis; Whitehouse Group (lower Katian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); two cranidia and a partial thoracopygidium; internal and external molds. This species has never been revised, and Reed’s (1914, pl. 6, figs 4–6) heavily retouched photographs are the only available illustrations. quincuncialis Whittard, 1961; Diacanthaspis; Meadowtown Formation (Darriwilian), Shropshire, England (Eastern Avalonia); one incomplete cranidium; internal mold. scitula Whittington, 1956; Diacanthaspis; Oranda Formation (Sandbian), Virginia, USA (Laurentia); cranidium with attached librigena, cranidia, librigenae, hypostome, thoracic segments, pygidia; silicified. secreta Whittington, 1956; Diacanthaspis; Edinburg Formation (Sandbian), Virginia, USA (Laurentia); cranidia, librigenae, thoracic segments, pygidia, protaspid; silicified. sladensis Reed, 1905; Acidaspis; Haverford Mudstone Formation (upper Katian), Pembrokeshire, Wales (Eastern Avalonia); cranidia and pygidia; internal and external molds. Photographically illustrated by Cocks and Price (1975, p. 712, pl. 83, figs 10–13). tariccoi Hammann and Leone, 2007; Diacanthaspis (Diacanthaspis); Portixeddu Formation (lower Katian), Sardinia, Italy (Corsica and Sardinia); cranidia, librigena, pygidia; internal molds and latex casts from external molds. trippi Owen in Harper and Owen, 1986; Diacanthaspis (Diacanthaspis); Balclatchie Formation (Sandbian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); dorsal exoskeletons; internal mold and latex casts from external molds. turnbulli Reed, 1905; Acidaspis (Ceratocephala); Sholeshook Limestone Formation (upper Katian), Pembrokeshire, Wales (Eastern Avalonia); dorsal exoskeleton, thoracopygidium, cranidium and associated thoracic segments; internal molds and latex cast from external mold. Revised by Price (1974, p. 864, pl. 116, figs 3–5). In addition to these formally named species, the following have been assigned in open nomenclature: Diacanthaspis sp. of Tripp (1980b, p. 156, pl. 1, figs 41–43), Craighead Formation (early Katian), South Ayrshire, Scotland (Laurentia affinity Midland Valley Terrane); Diacanthaspis (Diacanthaspis) sp. of Owen (1981, p. 71, pl. 17, figs 17, 19), Lunner Formation (late Katian), Hadeland, Norway (Baltica); Diacanthaspis sp. of Lu and Zhou (1981, p. 20, pl. 3, fig. 10), Tangtou Formation (early Katian), Jiangsu, China (South China) (see Tripp et al. [1989, p. 63]); Diacanthaspis sp. of Zhou et al. (1984, p. 33, fig. 8l), Shihtzupu Formation (Darriwilian), Guizhou, China (South China); Diacanthaspis sp. of Qu (1986 p. 304, pl. 2, fig. 6), Shichengzi Formation (late Katian), Gansu, China (Qaidam-Qilian Terrane); Diacanthaspis (Diacanthaspis) cf. conica of Hammann and Leone (2007, p. 90, pl. 51, fig. 10), Domusnovas Formation (late Katian), Sardinia, Italy (Corsica and Sardinia); Diacanthaspis sp. of Suzuki et al. (2009, p. 303, fig. 5U), Boda Formation (late Katian), Dalarna, Sweden (Baltica); Diacanthaspis sp. of Ghobadi Pour et al. (2011, p. 184, fig. 11b, c), Karagach Formation (Sandbian), East Kazakhstan Region, Kazakhstan (Şyŋğys–Tarbağatai Terrane). Discussion. As alluded to in the introduction, Diacanthaspis has become something of a wastebasket taxon for Ordovician odontopleurine species, and it currently includes species with a wide range of morphologies. As presently conceived it is unlikely to represent a clade. Resolution of its taxonomy is beyond the scope of the paper, but the Sandbian type species shares features with a handful of other Laurentian species of similar age that suggest a much pared down, phylogenetically meaningful, genus. Features include extreme spinosity, with cranidial sculpture featuring slender, elongate spines developed in place of simple tubercles in most other species (and, in fact, most species of the entire family) (e.g., Whittington, 1956, pl. 5, figs 1, 4, 7, 9, pl. 7, fig. 3, pl. 10, fig. 5, pl. 11, fig. 15, pl. 12, figs 1–3, 7, etc.). This characterizes the type species, D. cooperi, and is shared with D. lepidus, D. secretus, D. orandensis, and D. scitulus. These species also all have small spines on the dorsal aspect of the genal spine (e.g., Whittington, 1956, pl. 5, figs 7, 9, pl. 7, figs 7, 14). Their pygidia all feature major border spines that are only slightly longer than the other border spines (a condition found also in other species assigned to Diacanthaspis (s.l.)), and with all the spines having lateral fringes of tiny accessory spines (which seems to be unique to this group among Ordovician species) (e.g., Whittington, 1956, pl. 5, fig. 12, pl. 7, figs 8–10, pl. 10, figs 17–19, 27, pl.

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