Hintzeia Harrington, 1957

Mcadams, Neo E. B. & Adrain, Jonathan M., 2011, Systematics of the Lower Ordovician pliomerid trilobite Hintzeia, with species from the Great Basin, western USA, Zootaxa 2910, pp. 1-45 : 5-7

Hintzeia Harrington, 1957

Type species. Protopliomerops aemulus Hintze, 1953 (= Protopliomerops celsaorus Ross, 1951 ); by original designation. This species is from western Utah, USA, and is Tulean ( Hintzeia celsaora Zone ) in age.

Other species. Protopliomerops firmimarginis Hintze, 1953 (Tulean, Psalikilus spinosum Zone ); Hintzeia parafirmimarginis n. sp. (Tulean, Psalikilus spinosum Zone ); H. plicamarginis Simpson, Hughes , Kopaska- Merkel, and Ludvigsen, 2005 (early Tulean).

Diagnosis. Anterior border long, wide, strongly anteriorly bowed, with median arcuate anterior curve in posterior margin of most species; anterior surface of posterior wall of border exposed in anterior view. Glabella rectangular, very gently anteriorly tapered, with small LF partially obscured by anterior border. Palpebral lobes with widest part of arc opposite S2. Pygidium of five segments and small, triangular terminal piece. Pygidial spines short to medium-long, slightly to moderately splayed, and slightly laterally flattened; with dorsally recurved tips in some species.

Discussion. Simpson et al. (2005, p. 538) diagnosed Hintzeia as possessing an L1 which is larger than L2 or L3. However, their description of H. plicamarginis states that its lateral glabellar lobes are equally sized ( Simpson et al., 2005, p. 539), and this is true also of the other three species of Hintzeia . Simpson et al. (2005) also included "S3 anterior or posterior to lateral glabellar corners", but the location of S3 is likely symplesiomorphic, as many pliomerids (e.g., species of Pseudomera, Protopliomerella , and Lemureops McAdams and Adrain, 2009a) possess a similarly positioned S3. Further, the position of S3 is not variable among illustrated specimens of H. plicamarginis nor those of the species described herein, and whether its distal end is anterior or posterior to the "lateral glabellar corner" would appear to depend on how one defined such a feature. Hypostomal characters are excluded from the diagnosis because the species (with the exception of H. celsaora ) possess an apparently plesiomorphic, subrectangular hypostome with a long posterior border. The character "hypostomal lateral spines near posterolateral corners" is widely distributed among pliomerids, and is also shared with the cheirurid Rossaspis Harrington, 1957 (see Ross, 1951, pl. 31, figs 17, 18, 21, 22). Further, Edgecombe and Chatterton (1987, p. 345) considered that the seven marginal spines seen on pliomerid taxa such as Hintzeia are shared with some members of Encrinuridae Angelin, 1854 , and are likely indicative of a close relationship of Encrinuridae to Pliomeridae .

Hintzeia glabella Kobayashi, 1960 , was described from the Tremadocian Bunkoku Formation of South Korea. It is known only from a mold of a crushed partial cranidium, and as such is essentially a nomen dubium. It does not possess diagnostic features of Hintzeia , but its phylogenetic relationships cannot be confidently assessed without more material. Hintzeia taoyuanensis Liu in Zhou et al., 1977, from the Tremadocian Madaoyu Formation of Hunan, China (see also Liu, 1982), was reassigned to Protopliomerops by Peng (1990), who revised it on the basis of several articulated individuals and additional disarticulated material. We concur that it is not a species of Hintzeia , though Protopliomerops is a problematical taxon with a very poorly known type species.

Whittington (1961, p. 917) suggested that Hintzeia and the Dapingian (Whiterockian) taxon Kanoshia Harrington, 1957 , were "similar", and that Pseudomera cf. P. insolita ( Poulsen, 1927) of Hintze (1953) from the upper Blackhillsian resembled the type species of both Kanoshia and Hintzeia . Demeter (1973, p. 58) assigned K. kanoshensis and P. cf. P. insolita to Hintzeia , rendering Kanoshia a junior subjective synonym, and Laurie and Shergold (1996) agreed. Hoel (1999) removed Kanoshia from synonymy with Hintzeia , citing differences in glabellar furrows and the hypostomal margin. We concur that neither Kanoshia (which is likely a junior synonym of Pseudomera and which we will revise in a forthcoming work) nor any species of Pseudomera should be assigned to Hintzeia . Knowledge of the morphology of species of Pseudomera and Kanoshia has been compromised since Hintze (1953, pl. 23, figs 5–13, pl. 25, figs 5, 6, 8–12) misassociated the head and hypostome of his Cybelopsis cf. C. speciosa Poulsen, 1927 , with the tail of his Pseudomera cf. P. insolita and vice versa. Multiple occurrences of Pseudomera and Cybelopsis in upper Ibexian-Whiterockian strata at Ibex leave no doubt about the correct association, and Whittington (1961, pl. 100, fig. 17) also figured an articulated specimen of Pseudomera cf. P. barrandei ( Billings, 1865) from the Whiterockian upper Pogonip group of the Toquima Range, Nevada. The mistaken association and its phylogenetic and taxonomic ramifications will be addressed in detail in a forthcoming paper on Pseudomera .

Hoel (1999, p. 276) assigned Protopliomerops rossi Harrington and Leanza, 1957 , from the Tremadocian of Salta Province, Argentina to Hintzeia . Waisfeld and Vaccari (2003) also suggested that P. rossi was related to Hintzeia based on its lack of genal spines and the shape of the distal ends of the fixigenae. However, the short anterior border, lack of frontal areas, 14-segmented thorax, the presence of anterior pleural bands on all segments of its pygidium, and the posteriorly exposed terminal piece rule out its membership. Hoel (1999) also regarded the Floian species " Pliomerops " actinurus ( Dalman, 1824) from Sweden and Norway as a member of Hintzeia , considering that "it is not easy to find any difference between Hintzeia and Pliomerops Raymond, 1905 ." Pliomerops canadensis ( Billings, 1859) , the type species of Pliomerops from the Mingan Formation (Sandbian) of Quebec, bears little close resemblance to either "P." actinurus or to any member of Hintzeia . Among many other differences, Pliomerops canadensis possesses a thorax of 18 segments ( Shaw, 1968, pl. 2, fig. 3); that of " Pliomerops " actinurus has 14 segments ( Hoel, 1999, fig. 16D); and that of species of Hintzeia has 15 segments (Plates 8, 11). Further, "P." actinurus lacks the distinctive posteriorly indented anterior border of Hintzeia .

The identity of specimens of "P." actinurus is not entirely straightforward. The species was illustrated by Angelin (1878, p. 35, pl. 22, fig. 2) as Pliomera actinura ( Dalman, 1824) with a new species, Pliomera mathesii (p. 35, pl. 22, figs 1, 1a–1c). In these illustrations, " Pliomerops " actinurus and Pliomera mathesii are depicted as an articulated individuals very similar to the specimen figured by Hoel (1999, fig. 16D), although the specimen of "P." actinurus is approximately 70% as long as that of P. mathesii . Wiman (1908) examined museum collections and considered Pliomera mathesii a junior subjective synonym of "P." actinurus, stating that the former represented immature and tectonically deformed specimens of the latter. He also illustrated some specimens, which differ from Angelin's drawings in having a nearly square glabella with a median furrow on LF and a more widely splayed pygidium with shorter pleural spines. As both Angelin's and Wiman's illustrations are pen and ink, these differences could be due to drafting errors. However, Wiman's description states that the glabella is square and some specimens have a faint median LF furrow; the pygidium was not described in detail. Hoel's material and Angelin's drawing clearly show an elongate, ovoid glabella without a median LF furrow, and the pygidia are similar, though the pleural spines are longer on Angelin's drawing. These discrepancies leave open the possibility that several distinct species have been confused as " Pliomerops " actinurus.

Hintzeia sp. indet. of Laurie and Shergold (1996, p. 90, pl. 6, figs 1–6, 9–11; = Rossaspis sp. of Legg [1976]), from the Emanuel Formation (Floian), though not well preserved, is similar to Hoel's (1999) material of "P." actinurus, and in fact Hoel directly assigned the Australian material to the Baltic species. This is difficult to evaluate given the available material, but there seem to be several differences, including shorter, more downwardly curved pygidial spines in the Australian taxon. One pygidium assigned by Laurie and Shergold (1996, pl. 6, figs 7, 8) is not conspecific with the other material. Based on comparison with our new collections from western Laurentia, it represents an early species of the telephinid Carolinites Kobayashi, 1940 , and a closely similar Laurentian species will be described in a forthcoming work. " Pliomerops " actinurus, the Australian species, and " Protopliomerops " rossi are all similar to the early Whiterockian Pliomerops praematura Fortey, 1980 , from the Vallhalfonna Formation of Spitsbergen, Norway, but the relationship of these species to P. canadensis and other taxa needs to be examined via phylogenetic analysis.

Toro and Monaldi (1981) erected Benedettia with the type species based on a single partial cranidium from the Floian San Juan Formation of Argentina, and assigned it to the subfamily Protopliomeropinae Hupé, 1953. They considered that the closest comparison was to Kanoshia , citing a similarly shaped glabella but different glabellar furrows and sculpture. They also compared Benedettia with Hintzeia , considering that some (unspecified) morphological characteristics were similar, and they differentiated the genera in the shape of the glabella , position of S3, and the cranidial sculpture. Vaccari (2003) figured additional material, including pygidia, librigenae, and two articulated specimens of a second species. He considered that this new information showed that Benedettia is related to Canningella Legg, 1976 , and that together they are most likely closely related to a group of Floian-Darriwilian, mainly Laurentian taxa including Cybelopsis Poulsen, 1927 , and Ectenonotus Raymond, 1920 .

As noted above, Protopliomerella may cause paraphyly in Hintzeia , but we tentatively consider both genera valid until all species involved are revised and described, and a species-level phylogenetic analysis is conducted. Hintzeia firmimarginis , H. parafirmimarginis , and H. plicamarginis all possess a distinctive anteriorly bowed anterior border with a median anteriorly curved indentation in the posterior margin. Hintzeia celsaora does not; its bor- der is wide, but is subrectangular. This may be evidence of paedomorphosis, as the anterior border in juvenile cranidia of H. firmimarginis , H. parafirmimarginis , and H. plicamarginis describes a smooth curve, and the indentation develops and strengthens as size increases. Hintzeia celsaora possesses a shallow arc formed by the rostral suture on the median anteroventral rim of the anterior border, which is present to a much lesser extent in H. parafirmimarginis , and is not noticeable in large specimens of H. firmimarginis , but is observable on small cranidia (e.g., Pl. 1, fig. 25). This pattern also suggests paedomorphic development. The rostral suture arc is increasingly prominently developed in species of Protopliomerella (e.g., P. contracta Ross, 1951 , pl. 33, figs 17, 27) and Lemureops. It is also present in Pseudocybele altinasuta Hintze, 1953 , and it may be an important synapomorphy uniting these taxa. Other characters also suggest that H. celsaora at least may be more closely related to Protopliomerella. Its librigenae are narrow and elongate; its hypostome is strongly posteriorly tapered and the middle body is finely tuberculate; some thoracic segments possess a notch in the pleural spine; and the pygidium is short, with short, narrowly separated spines. This morphology is very similar to that of P. contracta and other species of Protopliomerella (unpublished data; see also undescribed species on figs 10, 11, 14, 15 of Adrain et al. [2009]).

Demeter (1973) figured numerous pliomerid sclerites collected from sections G, 1965 C and C-offset (approximately equal to Section D of Hintze [1951, 1953]; see Adrain et al., 2009, p. 546), and Mesa. Those relevant to Hintzeia but which cannot be assigned to a species are dealt with here. Assignments that can be confirmed are included in the synonymy and discussion of the appropriate species of Hintzeia below. Demeter's (1973, pl. 3, figs 15a–15c) Hintzeia sp. probably represents a species of Ibexaspis Přibyl and Vanĕk (1985) . The cranidia of his pl. 4, figs 1a–1c, 5, 9, 10 do not belong to (respectively) Kanoshia cf. kanoshensis or Pseudomera cf. P. insolita , both of which Demeter had also assigned to Hintzeia . The cranidia of pl. 4, figs 1a–1c and 5 belong to a new pliomerid genus and to Ibexaspis , respectively; those of pl. 4, figs 9, 10 are too poorly preserved to assign with any confidence. Ibexaspis will be revised with description of numerous new species in a forthcoming work. Demeter figured two pygidia and a hypostome (1973, pl. 5, figs 2, 3, 7) in open nomenclature. They resemble those of Hintzeia firmimarginis , but they occur in the much younger Heckethornia hyndeae Zone and belong to a plesiomorphic new species tentatively assigned to Cybelopsis .