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PARANACASTE PONTAGROSSENSIS POPP, 1989 (TRILOBITA: ACASTOIDEA): PROPOSED CONSERVATION OF THE TAXON
Journal of Paleontology, May 2006 by de Carvalho, Maria da Gloria Pires, Edgecombe, Gregory D
INTRODUCTION
THE PRESENT note aims to clarify the taxonomic status of the calmoniid trilohite Paranacasie pontagrossensis Popp, 1989, from the Ponta Grossa Formation. Lower Middle Devonian (Eifelian) of the Parana Basin, Brazil.
Paranacasie Popp, 1989 was ereeted as a monotypic genus based on P. pontagrossensis. Carvalho and Edgecombe ( 1991 ) described material from the Ponta Grossa Formation as Bainella pontagrossensis (Popp, 1989), considering it to be conspecilic with the types, and regarded Paranacasie as a subjective synonym of Hdiiielld Rennie. 1930.
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New specimens that clearly represent Paranacasie poniagrossensi.i demonstrate that the species is distinct from the Bainellu described and figured by Carvalho and Edgecombe (1991). Furthermore, the generic distinctness of Paranacasie can be upheld. The genus may be diagnosed based upon the cephalic margin being rounded medially, having a dense sculpture of mixed small tubercles and coarse granules (Fig. 1.1), the genae being bluntly angular and lacking a spiniform process, the thorax lacking axial spines, and the pygidium being small and semicircular, with an entire margin. The assignment of a rounded pygidium to P. pontagrossensis, questioned by Carvalho and Edgecombe (1991). is substantiated by the new material (Fig. 1.2). The genus remains monotypic, known only from its type species in the Ponta Grossa Formation.
Bainella is distinguished from Paranacaste by the following diagnostic characters: cephalon moderately to strongly arched (tr.); eye offset laterally, connected to axial furrow by ocular ridge; palpebral lobe elevated; LO prominently raised, usually with stout median spine; genae coarsely pilled; thoracic axial ring shortened medially, bearing transversely widened median spine; pygidium with posteroinedian spine in most species, exceptionally rounded. The Ponta Grossa material assigned to ttainella by Carvalho and Edgecombe (1991) is a member of that genus as diagnosed above. Because the Ponta Grossa Formation specimens of Bainella are no longer identified as conspecilic with P. pontagrossensis. a new specific name is proposed below.
Paranacaste was originally classified as an acaslid (Popp, 1989) on the basis of its having a bifurcate S1: obsolete S2 an S3; and pygidium being semicircular with an entire margin. Subsequent studies reassigned several alleged South American Silurian and Devonian acastids to the Calmoniidae (see Eldredge and Branisa, 1980; Lieberman et al., 1991; Edgecombe, 1993). In Paranacaste, the anterior branch of the facial suture transects the anterolateral corner of the frontal glabellar lobe, as observed in many calmoniids and a diagnostic feature of Calmoniinae, according to Struve (1959) (=Calmoniidae of more recent workers). Glabellar furrows S2 and S3 are not obsolete, but rather are narrow and shallow on the external mold (Fig. 1.1), as in many calmoniid genera. The small eyes and relatively long (exsag.) L1 of Paranacaste are typically calmoniid rather than acastid characters. In most calmoniids the pygidial margin bears spines or lappets as well as a posteromedian lappet or spine. However, an entire pygidial margin is observed in primitively acastomorph calmoniids such as Andinacaste Eldredge and Branisa, 1980, and within different non-acastomorph lineages (such as Tormesisus Waisfeld, Edgecombe, and Vaccari, 1994; Bainella gamkaensis Rennie, 1930; Cooper, 1982).
BAINELLA PARANAENSE new species
Bainella pontagrossensis (Popp, 1989). CARVALHO AND EDGECOMBE, 1991, p. 10, fig. 5a-e.
non Paranacaste pontagrossensis POPP, 1989, p. 25.
Diagnosis.-Bainella with cephalic margin smoothly rounded, axial region not bulging anterior to genae; frontal lobe gently inflated (sag., tr.); S2 and S3 moderately impressed; anterior edge of eye adjacent to axial furrow; extraocular gena broad (tr.); large "metagenal" process on cephalic posterior border; genal angle blunt.
Description.-see Carvalho and Edgecombe (1991, p. 10-11).
Etymology.-For Parana State, where the specimens were collected.
Types.-Holotype, Departamento Nacional de Producao Mineral (DNPM) 1708, internal mold of cephalon and articulated thoracic segment (Carvalho and Edgecombe, 1991, fig. 5c-e); paratype DNPM 1612, counterpart molds of partial cephalon (Carvalho and Edgecombe, 1991, fig. 5a, b).
Occurrence.-Ponta Grossa Formation, Tibagi Mb (late Emsian, Grahn et al., 2000), Paraná, Brazil.
REFERENCES
CARVALHO, M. G. P., AND G. D. EDGECOMBE. 1991. Lower-Early Middle Devonian Calmoniid trilobites from Mato Grosso, Brazil, and related species from Paraná. American Museum Novitates, 3022, 13 p.
COOPER, M. R. 1982. A revision of the Devonian (Emsian-Eifelian) Trilobita from the Bokkeveld Group of South Africa. Annals of the South African Museum, 89:1-174.
EDGECOMBE, G. D. 1993. Silurian Acastacean trilobites of the Americas. Journal of Paleontology, 67(4):535-548.
ELDREDGE, N., AND L. BRANISA. 1980. Calmoniid trilobites of the Lower Devonian Scaphiocoelia Zone of Bolivia, with remarks on related species. Bulletin of the American Museum of Natural History, 165:181-290.
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