taxonID	type	description	language	source
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	materials_examined	TYPE SPECIES. — Asaphus homfrayi Salter, 1866, by original designation, Lower Ordovician, upper Tremadocian Stage of Porthmadog, Gwynedd, North Wales, UK.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	discussion	REMARKS Asaphids’ taxonomy is a problematic field into systematic, mainly because effacement is regarded as one of the most polyphyletic characters among trilobites (Fortey & Shergold 1984; Turvey 2007). In addition, there are many different isoteline taxa in which effacement appears as a morphological trend (e. g., Jaanusson 1959; Nielsen 1995; Turvey 2007, among others). It is important to note that, as Asaphellus has become a “ wastebasket ” taxon for the Early Ordovician (mostly Tremadocian) asaphids, an excessive expansion of its diagnosis exacerbates the problem even more (Fortey & Owens 1987). However, some species indicate a wide range of intrageneric variation. Among them, A. whittardi (Bates, 1969) from South Wales (Fortey & Owens 1987) exhibits a remarkably prominently segmented pygidium for the genus, with 10 well-defined axial rings, 8 pairs of ribs, and visible interpleural furrows. Besides, its glabella is bounded by shallow but well impressed axial furrows. At the other extreme of morphological variability within the genus, in such species as A. yanheensis Yin in Yin & Shanji, 1978 (see Peng 1990) and A. isabelae n. sp., whose segmentation is nearly completely obscured by effacement, with the preglabellar furrow as an exception, because of it remains visible as a shallow furrow or a change in slope. Between these extremes, several species show very lightly impressed but discernible furrows, as in A. stenorhachis, or a diverse effacement, either of the cranidium or the pygidium. In this latter respect, A. cf. A. trinodosus Chang, 1949 from the Tremadocian of Tasmania (Jell & Stait 1985), has an effaced cranidium but a distinct pygidial axis bounded by well-defined axial furrows. In addition, there are other cases contributing to the variability of the genus. For instance, usually the pygidial axis decreases unevenly in width and tapers backwards, however, A. lugneensis Courtessole et al., 1985 and A. fezouataensis Vidal, 1998 are examples where the pygidial axis decreases in width evenly.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	materials_examined	MATERIAL. — The type material illustrated by Kobayashi (1935: pl. 9, figs 11 - 15) housed in the Smithsonian Museum (USNM- PAL 94136) comprises one cranidium, one free cheek, and two pygidia. This is refigured herein, except for the cranidium, which is lost, all from the type locality.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	discussion	REMARKS	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	description	From the reworked boulders of the Cardonal Formation, Waisfeld & Vaccari (2003) and Vaccari et al. (2010) reported at least two of the species listed by Kobayashi (1935): Kainella meridionalis and “ Kainella ” conica. Hence, it is highly probable that A. catamarcensis comes also from the boulders included in this unit. Alternatively, and less likely, A. catamarcensis might come from the debris flow deposits of the Devendeus Formation. The record of another Kainella species (K. cf. K. teiichii) in a boulder of coarse quartzitic sandstone of the Devendeus Formation (cf. Vaccari & Waisfeld 2010: figs 9.1 - 9.7) suggests that the provenance of A. catamarcensis from this unit cannot be ruled out. Unfortunately the holotype cranidium figured by Kobayashi (1935: pl. 11, fig. 11) is lost, hence, a possible comparison of this sclerite is restricted to Kobayashi’s drawing. We reillustrate here a free cheek and two pygidia from the type series. The material is fragmentary and poorly preserved. The free cheek is subtriangular and the genal spine is broken off, however, a medium size might be inferred considering the width of the base. Within the type material, we are uncertain whether the two pygidia are conspecific, and because one of them is a juvenile, we have selected the specimen illustrated in Fig. 6 A herein as the lectotype of A. catamarcensis. The latter is semicircular, convex, with a well-marked, anteriorly wide (tr.), and slightly funnel-shaped axis. The pygidium has a remarkably wide border (sag., exag., and tr.), being among the widest known in the genus; the doublure is wider than the border and strongly terraced. Harrington (1938) and Harrington & Leanza (1957) redescribed the species, and gave a diagnosis, but expanding the concept of A. catamarcensis including a wide array of features exhibited by different morphotypes from more than ten localities (from Salta, Jujuy, and La Rioja provinces) ranging in age from the Furongian to the late Tremadocian (cf. Waisfeld & Vaccari 2003). Also Hoel (1999) mentioned two morphological variants, one younger than the other, both assigned to A. catamarcensis among the illustrations provided by Harrington & Leanza (1957). The incomplete nature of some material largely prevents accurate comparisons and assignments, however, the shape and definition of the axis, the effacement of the axial rings and pleural furrows, and the wide border of the pygidium selected as the lectotypepygidium suggest that none of the specimens illustrated by these authors can be considered to be conspecific with A. catamarcensis. Harrington (1938: pl. 13, figs 3 - 6, 8 - 10, 16) referred several specimens from different localities to A. catamarcensis: the material illustrated in his figures 3 and 8 comes from the Quebrada de Iruya and it is possibly associated with K. meridionalis (according to the revision by Vaccari & Waisfeld 2010). The pygidium in Figure 3 resembles A. stenorhachis here defined, mainly in the indistinct segmentation and morphology of the border. The latter characters distinguish it from those of the lectotype of A. catamarcensis. The hipostomes (Harrington 1938: pl. 13, figs 4, 6) are from Angosto de Pascha, the type locality of A. catamarcensis, the one illustrated in Fig. 6 does not appear to belong to an Asaphellus species. The rest of the pictures assigned to A. catamarcensis in Harrington (1938: pl. 13) match with new species under study from Quebrada de Humacha and also some of them were discuss recently in Tortello & Esteban (2014).	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	description	Several of the specimens referred to A. catamarcensis by Harrington & Leanza (1957: figs 65.2, 4, 6; 64.4, 5, 6) come from the upper Tremadocian successions of the Quebrada de Coquena, Quebrada de Chalala, and Río Santa Victoria. They are apparently close to a new species that it is now under revision by the authors from the upper middle Tremadocian successions exposed in Quebrada de Humacha and Quebrada de Chalala, and also close to the recent published asaphids in Tortello & Esteban (2014). Likewise, the pygidia from Río Volcancito (La Rioja, Furongian, Parabolina (N.) frequens argentina Zone, Harrington & Leanza 1957: figs 65.3) are distinguished from that of A. catamarcensis in a fairly segmented, shorter, and wider axis. Finally, the pygidia from Quebrada Colorada (Iruya, K. meridionalis Zone), referred to A. catamarcensis by Harrington & Leanza (1957: pl. 64.1, 65. 1), differ from the lectotype pygidium in a more well-segmented axis and narrower border. Waisfeld & Vaccari (2003: pl. 22, figs 3 - 6) assigned to A. catamarcensis some material derived from a sandstone boulder of the Cardonal Formation in the Pascha-Incamayo region. This boulder comes from the alleged type locality of Kobayashi’s material and contains K. meridionalis. The pygidium figured by Waisfeld & Vaccari (2003: pl. 22, figs 4, 5) is similar to the lectotype in several respects, however, the axis is less-defined and more parallel sided; the border is incomplete but appears to be narrower than the lectotype. The pygidium of Waisfeld & Vaccari (2003: pl. 22, fig. 4, 5) is reinterpreted here as A. isabelae n. sp.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	materials_examined	HOLOTYPE. — CPBA (collection of the UBA – Universidad Nacional de Buenos Aires) no. 4165 (Harrington 1938: pl. 5, fig. 18; Harrington & Leanza 1957: fig. 93.3), Quebrada de Rupasca, Alfarcito region, Rupasca Member, Santa Rosita Formation, Santa Victoria Group, lower Tr 2. MATERIAL. — 57 fragmentary specimens including 3 partially complete individuals, 21 cranidia, 27 pygidia, 15 free cheeks, 8 specimens with thoracic segments, and 3 hypostomas. Illustrated material CEGH-UNC 25736 - 25748. OCCURRENCE AND AGE. — Quebrada del Arenal (levels from DLA 31 to DLA 37). Quebrada Rupasca, and Angosto de Chucalezna, J. Til. - 2 in Harrington & Leanza (1957). Quebrada Colorada and Angosto de Chucalezna, S. Iru. 4 in Harrington (1938). Rupasca Member, Santa Rosita Formation, Santa Victoria Group. Middle Tremadocian (Tr 2), B. tetragonalis Zone.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	description	EMENDED DIAGNOSIS. — Exoskeleton elongated and elliptical, about 70 % longer than wide. Cranidium smooth, glabella almost indistinct laterally, preglabellar furrow ill-defined, convex forward. Genal spines widely based, and short (about 20 % of free cheek maximum length). Pygidial border flat to slightly concave, wider anteriorly than posteromedially, barely defined axis in the anterior third of the pygidium. DESCRIPTION Cephalon semicircular, slightly convex, wide and depressed frontal area without differentiated anterior border, 1.8 times wider than long and 40 % of the total body length, wide (tr.) posterolateral projection. Lateral border broad and well- marked by a change in slope, posterior border defined by a wide (exsag.), shallow, and transverse posterior border furrow. Facial suture isoteliform, anterior branch slightly divergent in front of eyes, meeting anteriorly in a tiny ogive; posterior branch sigmoidal, runs outwards and backwards behind the eyes, and slightly inwards cutting posterior border close to the genal angle. Cranidium almost flat; palpebral, preocular, and postocular areas barely discernible. Preglabellar area flat, defined by a gentle change in slope, reaching about 15 % of cranidial maximum length (sag.). Wide posterior area of fixigena (exag., tr.). Glabella smooth, defined by indistinct axial furrows, with no differential convexity compared with the rest of the cranidium (Fig. 8 A, B); occipital ring reduced, poorly defined by a shallow furrow, slightly convex forward, set close to posterior margin. Median node located at about 1 ⁄ 5 of the cranidial maximum length from posterior margin. Palpebral lobe of medium size, flat, broadly arcuate, located at cranidial midlength, palpebral furrow nearly effaced; eye length (exag.) / cranidial maximum length (sag.) about 0.22 (n = 7). Free cheek subtriangular, broadly arcuate external margin; doublure subparallel to the margin, lateral border defined by broad and shallow furrow, diminishing in width and fading out towards genal angle, depressed with respect to genal field, border narrow and weakly convex. Genal spine broad-based, and short (about 20 % of the librigena length), strongly tapering and directed straight backwards (Fig. 8 B, E). Hypostoma elongate (sag.) and suboval, with rounded posterior margin; wide posterolateral borders with strong and closely spaced terrace lines. Median body gently convex, longer than wide, posterior lobe crescentic, maculae sharply impressed, transverse, and deep; anterior wings wide (tr.) and subrounded. Thorax with 8 segments, about the same length (sag.) as the pygidium, decreasing slightly in width (tr.) backwards. Axis weakly convex, about 35 % of the total width (tr.), defined by well impressed and slightly backwards-tapering axial furrows; articulating furrow narrow and deep; articulating half-ring short (tr.). Pleural region moderately wide (about 65 % of thoracic maximum width); pleural furrow deeper and wider medially, runs toward anterior margin of pleura, shallower and narrower adaxially, lightly impressed abaxially, anterior pleural band slightly wider (exag.) than posterior pleural band. Pleural extremities obliquely truncated and facing backwards, well-marked pleural fulcra. Pygidium slightly convex, about 55 % wider than long. Border flat, well-defined by a shallow furrow and a change in slope, decreasing progressively in width backwards, narrowest posteromedially. Anterolateral corner of pygidium (articulating facet) subtriangular. Inner margin of doublure subparallel to the margin. Fine and closely spaced terrace lines visible on doublure (on exfoliated material). Axis gently convex (tr., sag.), about 20 % of pygidial width, bounded by weak axial furrows, indistinct posteriorly (Fig. 8 E, G, K), almost effaced in some specimens (Fig. 8 I, J, L, M), evenly tapering backwards, posterior tip slightly raised, terminating in advance of border furrow. Articulating half-ring of even width, defined by a transverse furrow. 2 - 3 anterior axial rings slightly impressed in specimens preserved in mudstone, defined by narrow and shallow ring furrows, up to eight faint rings visible in some specimens (mostly internal moulds). Pleural field wide, subtriangular; inner part gently convex (tr.), then steeply curving down to border furrow; anterior halfrib well defined by distinct furrow, wider medially, abruptly terminating at border furrow, remainder ribs and furrows faint or indistinct.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	discussion	REMARKS Harrington (1938) erected Illaenus stenorhachis on the basis of a single pygidium with four attached thoracic segments from the Quebrada Rupasca (Alfarcito area). Later, Harrington & Leanza (1957: 183, 184) included in this species additional material from other localities of the Cordillera Oriental (Quebrada Lampazar and Quebrada Pingüiyal), and accommodated it in Illaenopsis Salter, 1867. Waisfeld & Vaccari (2003) noted that the holotype is an asaphid, and hence the name stenorhachis should be restricted to it. Although the holotype (Harrington 1938: pl. 5, fig. 18; Harrington & Leanza 1957: fig. 93.3) is slightly distorted, the Asaphellus material from the Quebrada del Arenal studied herein closely resembles it in an identical pygidial outline, mostly indistinct axial and pleural furrows (except for the first pleural furrow), and the uneven width of the border, wider laterally than posteromedially. Hence, the material from Quebrada del Arenal is referred herein to Asaphellus stenorhachis. Asaphellus stenorhachis is similar to the type species A. homfrayi Salter, 1866 from the late Tremadocian Garth Hill and Shineton Shale formations (North Wales and Shropshire, UK) (Lake 1942; Fortey & Owens 1991) in the general effacement of the exoskeleton and the anterior course of the facial suture with a similar variation range between the anterior and posterior branches (90 - 110 °). However, in A. stenorhachis the glabella is less defined laterally, the preglabellar field is narrower (sag., exsag.), the postocular fixigena is wider (tr.), the genal spine is shorter, the pygidial border is of uneven width (sag., exsag., tr.) and finally, the pygidial axis is less distinct and less raised above the pleural field. Several species of Asaphellus are known from north western Argentina. A. catamarcensis, herein restricted to the type material, distinguishes from A. stenorhachis in the pygidial outline, wider border, well-defined axis, and more segmented pleural fields.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF9AEC12CAB4FAA00B6CDDFB.taxon	description	The pygidium referred by Harrington (1938: pl. 13, fig. 3) to A. catamarcensis from Quebrada Colorada (Iruya area) resembles that of A. stenorhachis in several aspects, such as the general outline, degree of effacement, and shape of the border. It is possibly conspecific with A. stenorhachis, but better preserved material is required in order to be certain of this assignment. Suárez Soruco (1975: pl. 2, figs 1, 2) defined A. palquiensis from the Kainella andina Zone, lower Tremadocian (Tr 1) of South Bolivia (Vaccari et al. 2010). A. palquiensis differs from A. stenorhachis in a much longer genal spines, a better defined preglabellar area, and stronger segmentation of the pygidium. Among other non-Argentinean species of Asaphellus, Robison & Pantoja-Alor (1968) described three species from the Tiñú Formation (Tremadocian, Oaxaca, Mexico); of these, only A. artus bears some resemblance to A. stenorhachis The smoothness and posteromedian decrease in width of the pygidium of the latter, resembles the external moulds of the Mexican species (Robison & Pantoja-Alor 1968: pl. 99, figs 1 - 6), however, the exfoliated material of A. artus displays a well-defined and segmented pygidial axis, and distinctly furrowed pleural fields. Besides, A. artus has larger eyes, a well-defined frontal area, and larger genal spines. Another similar species is A. cf. graffi Thoral, 1946 (Fortey & Owens 1992: fig. 4) from the Habberley Formation (late Tremadocian, Welsh basin, UK), however, the outline of the pygidium, the well-defined axis, and a broader border clearly distinguishes it from A. stenorhachis. A group of Tremadocian species of Asaphellus from China described as A. inflatus Lu, 1959; A. tungtzuensis Sheng, 1958; and A. yanheensis Yin in Yin & Shanji, 1978) from the Nantsinkwan Formation of the Yangtze Platform (Peng 1990) display a very faint segmentation in the pygidium, thus resembling A. stenorhachis, however, the hypostoma of the latter has a non-terraced median body and more marked cephalic and pygidial borders defined by a change in slope. The nature of the pygidial border of A. acutulus Zhou & Zhang, 1985 from the Tremadocian of the Jilin region, northeast China, closely resembles that of A. stenorhachis (particularly the specimens illustrated by Zhou & Zhang 1985: pl. 10, figs 7, 8), nonetheless, considering several differences in the cranidial features, the general outline of the pygidium, the axis that is not funnel-shaped and decreases steadily backwards in width, distinguishes this from A. stenorhachis.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF91EC11CAE9FF630AA9DC9A.taxon	description	(Figs 7 G; 9 B; 10)	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF91EC11CAE9FF630AA9DC9A.taxon	materials_examined	HOLOTYPE. — CEGH-UNC 25751 (Fig. 10 E). Type horizon DLA 28, lower Tr 2, Quebrada del Arenal creek, lower Rupasca Member, Santa Rosita Formation, Santa Victoria Group. MATERIAL. — 140 fragmentary specimens, including 1 partly complete individual, 20 cranidia, 48 pygidia, 28 free cheeks, 7 specimens with thoracic segments, and 12 hypostomas. Illustrated material CEGH-UNC 25749 - 25761. OCCURRENCE AND AGE. — DLA 28, DLA 29, DLA 30, lower part of the Rupasca Member, Quebrada del Arenal, K. teiichii Zone, middle Tremadocian (Tr 2); reworked boulder of the Cardonal Formation, Pascha-Incamayo area, K. meridionalis Zone, lower Tremadocian (Tr 1).	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF91EC11CAE9FF630AA9DC9A.taxon	etymology	ETYMOLOGY. — After FR Meroi Acerito’s grandmother Isabel Olivares. D IAGNOSIS Flat and large species of Asaphellus. Cuticle very thin, high degree of smoothness and effacement, except for the lightly impressed preglabellar furrow, pygidial axis indistinct.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF91EC11CAE9FF630AA9DC9A.taxon	description	DESCRIPTION Exoskeleton large, subelliptical and flat. Isopygous with flat cephalic and pygidial borders. Cephalon semicircular, with wide border, diminishing in width towards the genal angle. Doublure subparallel to the margin. Cranidium depressed or flat; axial furrow indistinct. Glabella almost indistinguishable, faint traces of convex anterior preglabellar furrow in some specimens (Fig. 10 E, F). Wide and subtriangular (exsag.) posterolateral projection. Posterior border and occipital ring reduced, poorly defined, and very close to posterior margin. Palpebral lobes of medium size, located at cranidial midlength. Anterior section of facial suture diverges gently forwards, bends smoothly adaxially, and converges medially to form an obtuse point sagittally in an ogive. Posterior section of facial suture curves backwards, bends downwards and slightly inwards at the level of the posterior border. Free cheek long and relatively narrow, subtriangular with rounded external margin. Broad-based and long genal spine (55 % of the total librigena length), slightly divergent from external margin. Hypostoma elongated, oval in outline (sag.), with rounded posterior margin. Wide posterolateral border, with fine terraced lines. Median body widest (tr.) at midlength, anterior lobe convex (sag., tr.), posterior lobe short (sag.), crescentic, maculae transverse, sharply impressed. Thorax incompletely known; almost indistinguishable from A. stenorhachis but less convex. Axis weakly convex, about 35 % of the total width (tr.), defined by well impressed and slightly backward-tapering furrows; articulating furrow narrow and deep; articulating half-ring short (tr.). Pleural region moderately wide (about 65 % of thoracic maximum width); pleural furrow deeper and wider medially, runs toward the anterior margin of pleura, shallower and narrower adaxially, lightly impressed abaxially. Pleural extremities obliquely truncated and backward-facing, faint marked pleural fulcra. Pygidium of very low convexity, 57 % wider than long (n = 14), border and border furrow indistinct. Doublure evenly wide, about 10 % length of pygidium (n = 11), subparallel to the pygidial margin along its extension. Anterior half-ring narrow (sag.), slightly convex forward. Articulating facet subtriangular, long (tr.). Anterior half-rib defined by narrow and shallow pleural furrow, remaining pleural furrows and ribs not visible.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF91EC11CAE9FF630AA9DC9A.taxon	discussion	REMARKS Asaphellus isabelae n. sp. appears to represent an extreme in effacement, flatness, and reduction of the cuticle thickness within the group. The latter character is noteworthy, as even the sediment roughness is reproduced on the surface of the exoskeleton. Despite effacement complicates taxonomy, the extreme smoothness and flatness might be considered as an autoapomorphic character for this species. Such a combination of characters has seldom been recorded in other Asaphellus species. For example, Asaphellus yanheensis Yin in Yin & Shanji, 1978 (Peng 1990: pl. 7, figs 6 - 13) from the Nantsinkwan Formation (Tremadocian, NW Hunan, China) exhibits a thorough effacement, with blurred furrows either in the cranidia or pygidia. Though the pygidium of the Chinese species exhibits great resemblance to A. isabelae n. sp., the cranidium of the former differs in several significant respects, such as a better defined anterior ogive, a median node that is placed more forwardly, a subparallel preocular facial sutures, and postocular sutures running straight backwards. Other species also show effacement either on the cranidium or the pygidium. Asaphellus tungtzuensis (Sheng 1958) (Peng 1990: pl. 8, figs 1, 2) from the Tremadocian of north west Hunan resembles A. isabelae n. sp. in the general effacement of the cranidium, however, the pygidium shows traces of axial furrows delimiting a weak axis along its length. The cranidium of Asaphellus cf. A. trinodosus Chang, 1949 (Jell & Stait 1985) from the Florentine Valley Formation (Tremadocian, Tasmania) is largely effaced; however, the pygidial axial furrows distinctly outline a convex axis. Among the Argentinean species of Asaphellus, only A. stenorhachis (see above) exhibits a general effacement though not to the degree of that of A. isabelae n. sp. Asaphellus stenorhachis differs from the new species in the higher convexity mainly of the pygidium, a better definition of the pygidial axis in its anterior third, and the presence of some furrows, lightly impressed but discernible (for instance the border furrows in the cephalon and pygidium).	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF92EC10CD15F966085CDFDA.taxon	description	(Fig. 7 C-F)	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF92EC10CD15F966085CDFDA.taxon	materials_examined	MATERIAL. — 4 pygidia; 1 fragmentary pygidium with attached thorax and free cheek. CEGH-UNC 25765 - 25767. OCCURRENCE AND AGE. — Horizon DLA 20, DLA 25. Upper Alfarcito Member and lower Rupasca Member of the Santa Rosita Formation, Santa Victoria Group. Late Tr 1 and early Tr 2.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF92EC10CD15F966085CDFDA.taxon	discussion	REMARKS This species is scanty in our samples; it differs from all others described herein in a semicircular outline, a well-defined wide axis, with up to five rings visible on some specimens, a well-defined border, and a wide subparallel doublure (on average about twice wider than the border). Specimens of this morphotype have been referred to A. catamarcensis by different authors, among them, one pygidium illustrated by Harrington (1938: pl. 13, fig. 10) from Angosto de Parcha (Pascha-Incamayo area, Salta), and two pygidia figured by Harrington & Leanza (1957: fig. 65.7, 8) from Sierra de Mojotoro (Quebrada de los Canchos, Caldera Department, Salta). Later, Tortello & Rao (2000), Tortello et al. (2002), Aceñolaza et al. (2003), and Tortello & Aceñolaza (2010) accommodated the material from Angosto de Lampazar (Pascha- Incamayo area) and Abra de Zenta in A. catamarcensis, based on the resemblance with the pygidia from Sierra de Mojotoro that Harrington & Leanza (1957: pl. 65, figs 7, 8) referred to that species. However, the type pygidium of A. catamarcensis reillustrated herein differs from these previous assignments (see A. catamarcensis remarks). In addition, the cranidium refer in Tortello & Aceñolaza (2010: figs 4 a, b) doubtfully could be assigned to Asaphellus (see A. catamarcensis remarks). Thus, we refer the material mentioned above tentatively to Asaphellus sp. 1. Nonetheless, additional material would be required in order to be certain about the generic assignment of this material.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF93EC10C87DF9A60C1ADE99.taxon	description	(Fig. 7 A, B)	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF93EC10C87DF9A60C1ADE99.taxon	materials_examined	MATERIAL. — Two pygidia CEGH-UNC 25763, 25764. OCCURRENCE AND AGE. — Horizon DLA 28. Lower part of the Rupasca Member, Quebrada del Arenal, K. teiichii Zone, Santa Rosita Formation, Santa Victoria Group, middle Tremadocian (Tr 2).	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF93EC10C87DF9A60C1ADE99.taxon	description	DESCRIPTION Pygidium semicircular, 60 % wider than long, gently convex with a well-defined, flat border of uniform width. Axis defined by narrow and well impressed axial furrows, about 18 % of maximum pygidial width, raised above pleural fields, increasingly elevated above pleurae posteriorly, tapering backwards and funnel shaped, with rounded posterior tip, terminating in advance of border furrow; three anterior axial rings barely visible. Broad (tr.) and gently convex pleural field, with faint indication of 3 - 4 pleural furrows, inner part gently convex (tr.), steeply sloping down to border abaxially. Inner margin of doublure subparallel to the pygidial margin.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
480E87D9FF93EC10C87DF9A60C1ADE99.taxon	discussion	REMARKS Asaphellus sp. 2 resembles A. catamarcensis (as revised herein) mainly in the definition of the axis and in being well raised above pleural field. However, the pygidial outline is 61 % wider than long, the axis is more parallel-sided, the border is wider, and the doublure widens posteromedially (lying well in advance of the posterior tip of the axis). The well-defined and raised pygidial axis and the evenly wide border clearly distinguish this material from A. stenorhachis and A. isabelae n. sp. The latter occurs in the same beds in the Quebrada del Arenal. Also, Asaphellus sp. 2 differs from A. kayseri (Kobayashi, 1937) (Waisfeld & Vaccari 2003) in a poorly segmented axis and pleural field, and a wider border. The Argentinean material resembles Asaphellus? sp. from the Saint-Chinean Formation, lower Tremadocian, Montagne Noire (Vidal 1996), however, Asaphellus sp. 2 exhibits a narrower border and doublure. Also, Asaphellus sp. 2 is close to Asaphellus sp. 1 (herein) and A. verus (Zhou & Fortey 1986, Upper Yehli Formation, Tremadocian, Hebei province, China), however, Asaphellus sp. 2 differs from both in a more marked, more convex, and less funnel-shaped axis. In addition, the doublure is subparallel to the border in Asaphellus sp. 2, instead of slightly subtriangular as in Asaphellus sp. 1.	en	Arcerito, Facundo René Meroi, Waisfeld, Beatriz, Balseiro, Diego (2015): Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina). Geodiversitas 37 (2): 131-150, DOI: 10.5252/g2015n2a1, URL: http://dx.doi.org/10.5252/g2015n2a1
