Geobios 35 (2002) 111Ð125 www.elsevier.com/locate/geobios

Hoplolichoides, Allolichas, Autoloxolichas and Akantharges, and the classification of lichid trilobites Hoplolichoides, Allolichas, Autoloxolichas et Akantharges, et la classification des trilobites Lichidae David J. Holloway a,*, Alan T. Thomas b

aInvertebrate Palaeontology, Museum Victoria, PO Box 666E, Melbourne, Victoria 3001, Australia bSchool of Earth Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom Received 9 November 2000; accepted 24 July 2001

Abstract

Hoplolichoides PHLEGER, 1936 and Autoloxolichas PHLEGER, 1936 are revised based on redescription of their type species, H. conicotuberculatus (NIESZKOWSKI, 1859) and A. sanctamathiae (SCHMIDT, 1885) respectively. Hoplolichoides is considered to be most closely related to Hoplolichas DAMES, 1877, and both are included in a revised Homolichinae. Autoloxolichas is restricted to its type species, and other species previously assigned to the genus are placed in Allolichas KRUEGER, 1992, the concept of which is expanded. Autoloxolichas and Allolichas are included together with three other genera and subgenera in the Subfamily Platylichinae, previously considered to be a junior synonym of Homolichinae. The hypostomal morphology previously regarded as important in uniting homolichine and platylichine genera is now regarded as primitive for the Lichidae. Metopolichas GÜRICH, 1901, previously included tentatively in the Homolichinae on the basis of its hypostomal morphology, is reassigned tentatively to the Lichinae. The trochurine ‘Acanthopyge’ erbeni MEISCHNER, 1965, from the Givetian of Germany, is assigned to Akantharges PHLEGER, 1936, permitting clarification of the pygidial morphology of the genus. Akantharges and Ceratarges GÜRICH, 1901 are unique amongst lichids in having a curved, transverse ridge on the posterolateral cranidial lobe, suggesting that these genera may have been derived from a common ancestor. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

Résumé

Les genres Hoplolichoides PHLEGER, 1936 et Autoloxolichas PHLEGER, 1936 sont révisés sur la base d’une redescription de leurs espèces types respectives: H. conicotuberculatus (NIESZKOWSKI, 1859) et A. sanctamathiae (SCHMIDT, 1885). Hoplolichoides est considéré comme le genre le plus proche de Hoplolichas DAMES, 1877. Les deux genres sont inclus dans les Homolichinae également révisés. Autoloxolichas ne contient que son espèce-type et d’autres espèces rapportées aurapavant à Autoloxolichas sont placées dans Allolichas KRUEGER, 1992 dont la définition est ainsi étendue. Autoloxolichas et Allolichas sont inclus avec trois autres genres et sous-genres dans la sous-famille des Platylichinae que l’on considérait avant comme un synonyme des Homolichinae. La morphologie de l’hypostome considérée autrefois comme importante (unissant les genres homolichines et platylichines) est à présent considérée comme primitive pour les Lichinae. Metopolichas GÜRICH, 1901 qui avait été placé dans les Homolichinae sur la base de sa morphologie hypostomale est placé dans les Lichinae. Le trochuriné ‘Acanthopyge’ erbeni MEISCHNER, 1965 du Givétien de l’Allemagne est attribué à Akantharges PHLEGER, 1936 permettant une classification de la morphologie pygidiale du genre. Akantharges et Ceratarges GÜRICH,

* Corresponding author. E-mail addresses: [email protected] (D.J. Holloway), [email protected] (A.T. Thomas).

© 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. PII:S0016-6995(02)00014-1 112 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125

1901 sont uniques chez les lichidés par leur crête transversale courbe sur le lobe cranidial postéro-latéral, suggérant que ces deux genres dérivent d’un ancêtre commun. © 2002 E« ditions scientifiques et médicales Elsevier SAS. Tous droits réservés.

Keywords: Trilobites; Lichidae; Systematics; Ordovician; Devonian

Mots clés: Trilobites; Lichidae; Systématique; Ordovicien; Dévonien

1. Introduction species of Akantharges from the Devonian of Morocco was illustrated by Thomas and Holloway (1988, pl. 14, figs 299, The trilobite genera Hoplolichoides, Autoloxolichas and 200, 303), who based their concept of the genus largely on Akantharges, all erected by Phleger (1936), were reviewed that specimen. We have subsequently been able to examine by Thomas and Holloway (1988) in their revision of the the material of ‘Acanthopyge’ erbeni MEISCHNER, 1965 Lichida. Additional information on these genera has become from the Givetian of Germany, and recognised that this available subsequently, providing the opportunity to clarify species belongs to Akantharges. The specimens of erbeni their taxonomic concepts as well as to assess their likely are relatively well preserved and clarify some of the relationships. In the light of our new data, we assign characters of the genus, particularly pygidial characters. Hoplolichoides to a revised Homolichinae. The Subfamily Platylichinae is resurrected to accommodate Allolichas and Autoloxolichas, together with other genera. 2. Systematic palaeontology Hoplolichoides has not generally been accepted as a distinct genus, most authors (Warburg, 1939; Hupé, 1953; Morphological terminology used here is that of Thomas Tripp, 1957, 1959; Balashova, 1960) considering it to be a and Holloway (1988). Stratigraphical nomenclature follows junior subjective synonym of Hoplolichas DAMES, 1877. the revised Ordovician series proposed by Fortey et al. Thomas and Holloway (1988) recognised Hoplolichoides (1995, 2000). but expressed reservations about its utility as an indepen- Several of the species dealt with herein were documented dent genus, stating that the pygidial morphology was by Schmidt (1885). Until recently, the specimens from this insufficiently known for a full comparison with other and other parts of Schmidt’s series of trilobite monographs genera. In the present paper, we redescribe cephala and were not available for study. Photographs of most of pygidia of the type species, H. conicotuberculatus (NIESZ- Schmidt’s specimens are now available on the World Wide KOWSKI, 1859), and compare it with other species con- Web at the site entitled ‘Catalogue of the trilobites figured in sidered to be congeneric, showing that Hoplolichoides Friedrich Schmidt’s ‘Revision der ostbaltischen silurischen warrants recognition as a separate genus. Trilobiten’ (1881Ð1907)’ by D.L. Bruton, O.A. Hoel, Autoloxolichas was based on Lichas sanctamathiae L.T. Beyene and A. Yu. Ivantsov (internet address SCHMIDT, 1885, and that was the only species listed by http://www.toyen.uio.no/palmus/schmidt/index.html). The Phleger (1937) as belonging to the genus. The genus was specimens are also listed but not illustrated in Bruton et al. briefly diagnosed by Phleger (1936) as differing from (1997). Platylichas in lacking the continuation of the longitudinal Repositories of specimens are denoted by the following furrow behind the bullar lobe, but Öpik (1937) dismissed abbreviations: CNIGR, Central Scientific-Research Geo- this supposed difference as being due to a misunderstanding logical Exploration Museum named after F.N. Chernyshev, and placed sanctamathiae in Platylichas. Tripp (1957, St Petersburg; GIE, Institute of Geology, Tallinn Technical 1959) and Dean (1974) also considered Autoloxolichas to be University; Gö, Geologisch-Paläontologishes Institut und a junior synonym of Platylichas. Thomas and Holloway Museum, Georg-August-Universität, Göttingen; MB, Mu- (1988) recognised Autoloxolichas as a distinct genus to seum für Naturkunde, Humboldt Universität, Berlin; RM, which they assigned, in addition to sanctamathiae, a num- Naturhistoriska Riksmuseet, Stockholm. ber of species resembling ‘Lichas’ laxatus MCCOY, 1846. Family: LICHIDAE Hawle & Corda, 1847 We now believe, based on the study of plaster replicas of the Subfamily: HOMOLICHINAE Phleger, 1936 type material of sanctamathiae, that Autoloxolichas should Diagnosis – S1 effaced or almost effaced, so that bullar be restricted to that species, and that the other species lobe is more or less completely fused with L1b; resulting included in the genus by Thomas and Holloway (1988) composite lobe circumscribed by furrows, except in Leioli- should be placed in Allolichas KRUEGER, 1992, the chas which has longitudinal furrow effaced externally. concept of which should be expanded. Palpebral lobe narrow, of almost uniform width throughout, Akantharges was until relatively recently known only moderately curved in outline. Hypostome with middle body from the type species, Lichas gourdoni BARROIS, 1886, as wide across posterior lobe as across anterior lobe, or the material of which is strongly deformed and difficult to wider; shoulder situated level with posterior border furrow; interpret. A well preserved cranidium of an undescribed border greatly expanded and flap-like at and behind D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 113 shoulder. Pygidium with two to three pairs of pleural furrows and six to eight marginal spines (spines absent in Leiolichas); anterior and posterior pleural bands flattened. Genera included Ð Homolichas SCHMIDT, 1885; Conolichas DAMES, 1877; Hoplolichas DAMES, 1877; Hoplolichoides PHLEGER, 1936; Leiolichas SCHMIDT, 1885; Otarozoum THOMAS & HOLLOWAY, 1988. Remarks Ð S1 is effaced, or almost so, in Conolichas, Hoplolichas, Hoplolichoides and Otarozoum, the bullar lobe almost completely fusing with L1b. The resulting composite lobe is circumscribed by the longitudinal and axial furrows, and by the transverse furrow in front of L1a (Fig. 1.1Ð4). The longitudinal furrow is effaced externally in Leiolichas but is present on internal moulds, though very shallow posteriorly (see Warburg, 1939, pl. 3, figs 7, 8). On some internal moulds of Leiolichas cranidia, S1 is also present but very weak. It meets the axial furrow just behind the intersection of the latter with the palpebral furrow, and is directed strongly obliquely backwards towards the point at which the longitudinal furrow abruptly shallows (Fig. 1.5). This glabellar structure is different from that in genera such as Platylichas, Autoloxolichas and Metalichas, which were previously included in the Homolichinae (Tripp, 1957, 1959; Thomas and Holloway, 1988), but which we now Fig. 1. Cranidial morphology in Homolichinae (1-5) and Platylichinae place in the Platylichinae (see below). In these genera, the (6-8). 1. Conolichas (after Thomas and Holloway 1988, pl. 7, fig. 141). 2. Hoplolichas (after Thomas and Holloway 1988, pl. 8, fig. 155). 3. axial furrow is effaced alongside L1b, and the bullar lobe is Hoplolichoides (after Fig. 2.6). 4. Otarozoum (after Thomas and Holloway circumscribed by the longitudinal furrow, S1, and the short 1988, pl. 8, fig. 161). 5. Leiolichas (after Thomas and Holloway 1988, pl. section of axial furrow between the anterior end of the 7, fig. 147). 6. Platylichas (after Warburg 1939, pl. 11, fig. 1c). 7. longitudinal furrow and the outer end of S1 (Fig. 1.6Ð7). Autoloxolichas (after Fig. 3.1 and Thomas and Holloway 1988, pl. 10, fig. Metopolichas GÜRICH, 1901 was tentatively included in 213). 8. Allolichas (after Thomas and Holloway 1988, pl. 10, fig. 188 and Krueger 1992, pl. 1, fig. 1b). Dashed lines indicate furrows that are very the Homolichinae by Thomas and Holloway (1988) by weakly developed, or present only on internal moulds; see text for details. weighting its hypostomal morphology, despite the fact that Non-standard abbreviations: af, axial furrow; b, bullar lobe; cl, composite it resembles Lichas and some other Lichinae in glabellar lobe; lf, longitudinal furrow; of, occipital furrow. structure (longitudinal furrow not generally extending be- Morphologie du cranidium chez les Homolichinae et les Platylichinae. 1. hind S1, with which it is united in a curve; S1 commonly Conolichas (d’après Thomas et Holloway 1988, pl. 7, fig. 141). 2. Hoplolichas (d’après Thomas et Holloway 1988, pl. 8, fig. 155). 3. incomplete abaxially). The hypostome of Metopolichas Hoplolichoides (d’après Fig. 2.6). 4. Otarozoum (d’après Thomas et resembles those of Homolichinae and some Platylichinae, Holloway 1988, pl. 8, fig. 161). 5. Leiolichas (d’après Thomas et Holloway rather than Lichinae, in being wider than long and having a 1988, pl. 7, fig. 147). 6. Platylichas (d’après Warburg 1939, pl. 11, fig. 1c). deep posterior border furrow (see Thomas and Holloway, 7. Autoloxolichas (d’après Fig. 3.1 et Thomas et Holloway 1988, pl. 10, fig. 1988, pl. 11, figs 227, 231, 235). However, hypostomes of 213). 8. Allolichas (d’après Thomas et Holloway 1988, pl. 10, fig. 188 et Krueger 1992, pl. 1, fig. 1b). Les hachures indiquent des sillons très Tetralichinae (e.g. Thomas and Holloway, 1988, pl. 12, figs faiblement développésouprésents seulement sur les moules internes. 250, 267) and Trochurinae (e.g. Chatterton and Ludvigsen, Abbréviations non standards: af, sillon axial; b, lobe bulleux; cl, lobe 1976, pl. 19, figs 17Ð20) also share these character states, composé; lf, sillon longitudinal; of, sillon occipital. which we now consider primitive for lichids as a whole and thus not useful for inferring relationships within the family. or wider, instead of narrower; the border is more expanded The interpretation of these character states as primitive is in width at the shoulder, where it has a flap-like appearance; supported by their presence in the oldest known lichid, and the shoulder is situated somewhat farther back, opposite Metopolichas? klouceki (RUû Zˇ ICˇ KA, 1926) from the lower the posterior border furrow rather than opposite the middle Tremadoc of the Czech Republic (see Thomas and Hollo- furrow or the posterior lobe of the middle body (compare way, 1988, pl. 11, fig. 236). In view of the similarities in Thomas and Holloway, 1988, pl. 10, fig. 196 and Fig. 3.4 glabellar structure between Metopolichas and some Lichi- herein). nae we now assign the genus to that subfamily. In comparing the thoracic and pygidial structure of Notwithstanding their similarity in the primitive charac- lichines and Platylichas, Whittington (in press) noted that in ter states mentioned above, hypostomes of Homolichinae both the inner parts of the thoracic pleurae are wide and differ from those of Platylichinae in that the middle body is evenly inflated, and the pleural furrows extend almost to the as wide across the posterior lobe as across the anterior lobe, pleural tips. The pygidial pleural bands in these taxa are of 114 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 similarly low convexity, are divided by the pleural furrow, Neben and Krueger, 1971, pl. 35, figs 15, 17). Of these and are extended distally into the marginal spines. This kind similarities, we do not attribute great taxonomic importance of thoracic and pygidial structure occurs in homolichines to the presence or absence of occipital spines, while the also (e.g. Otarozoum, see Thomas and Holloway, 1988, pl. weak differentiation of L1b may be a primitive character 8, figs 167Ð170) and, by comparison with other trilobites, state, compared with the condition in Conolichas and probably represents the primitive condition for the Lichidae. Otarozoum (in which L1b is indistinguishable), and thus not The pygidial pleural bands of Hoplolichoides are more indicative of close relationship. On the basis of the pygidial inflated than is usual for a member of these subfamilies, and similarities, however, we consider Hoplolichas to be most the genus is derived in that regard. closely related to Hoplolichoides. Hoplolichas differs from Genus Hoplolichoides PHLEGER, 1936 Hoplolichoides in that the glabella is more convex (sag., Type species Ð Lichas conico-tuberculata NIESZ- exsag.), the frontal lobe being more inflated and markedly

KOWSKI, 1859, from the Kukruse Stage (C2, lower Cara- overhanging the anterior border in palpebral view; the doc) of Estonia; original designation. minimum width of the median lobe is greater (rather than Other species Ð H. curvifrons (WARBURG, 1939); H. less) than the width of the bullar lobe measured across the furcifer (SCHMIDT, 1885). same transverse line; and the pygidium is not as transverse. Stratigraphical and geographical range Ð Middle In addition, pygidia of Hoplolichas species typically have LlanvirnÐlower Caradoc; Russia (St Petersburg district), much longer marginal spines, there is no spine situated Estonia, Sweden, Norway. immediately behind the second spine, and the posterior pair Diagnosis Ð Homolichine having glabella with L1b in- of spines are situated very close together, commonly being distinctly differentiated from bullar lobe by slight backward fused proximally (e.g. Thomas and Holloway, 1988, pl. 8, deflection and/or shallowing of longitudinal furrow, and fig. 162). very weak S1. Frontomedian and bullar lobes moderately Otarozoum resembles Hoplolichoides in the moderate convex (sag., exsag.), frontal lobe slightly overhanging cranidial convexity and the proportions of the glabellar medial part of anterior border in palpebral view; bullar lobe lobes, but differs in the absence of large occipital spines; with long axis subparallel to sagittal line; minimum width of L1b is not differentiated at all from the bullar lobe; the median lobe less than width of bullar lobe measured across cranidial tuberculation is much finer; there is no pygidial same transverse line. Occipital ring strongly elevated medi- border; the third pygidial pleural furrow is impressed; the ally, with large paired spines. Cranidial tuberculation very third pair of pygidial marginal spines is situated very close coarse. Pygidium transverse, approximately 160% as wide together; and the pygidium has no posteromedian spine. The as long (sag.), with three pairs of marginal spines and small pygidium of Otarozoum is very similar to that of Conoli- posteromedian spine; third pair of spines very short and chas, suggesting that these genera are most closely related broad, subtriangular or lobate, situated very close to second to each other. pair of spines. Axis approximately 30% maximum pygidial Apart from conicotuberculatus and furcifer, Phleger width anteriorly and 50% sagittal length. Pleurae with (1937) also included in Hoplolichoides the species Lichas prominent border that is transverse between second pair of (Hoplolichas) plautini SCHMIDT, 1885, L. (H.) longispina spines; first two pleural furrows and furrow defining post- [sic] SCHMIDT, 1885 and Lichas media [sic] POMPECKI, axial band terminating at inner edge of border; third pleural 1890. The last two belong to Hoplolichas, as indicated by furrow not defined; anterior and posterior pleural bands well the proportions of the glabellar lobes, the strongly over- rounded (exsag.). hanging frontal lobe and the large, unpaired occipital spine Remarks Ð Large paired occipital spines are preserved in the illustrated cranidium of medius (Pompecki 1890, pl. only in the type species, the occipital ring being incomplete 2, fig. 25, 25a), and the three pairs of long marginal spines, posteriorly in known specimens of the other two species the posteriormost pair situated fairly close together, in the assigned to the genus. We would not exclude a species from holotype pygidium of longispinus (Schmidt 1885, pl. 2, fig. Hoplolichoides solely on the absence of these spines. 25). In plautini, Schmidt (1885, pl. 2, figs 17Ð24) associated Hoplolichoides shows the greatest similarities with cranidia and an incomplete cephalon of Hoplolichas type Hoplolichas and Otarozoum. The similarities with Hoploli- with pygidia having the morphology of Hoplolichoides.We chas include the presence of large occipital spines (unpaired consider these pygidia to belong to Hoplolichoides furcifer, in Hoplolichas), the weak differentiation of L1b by a a species based on cranidia from the same locality and backward deflection of the longitudinal furrow and a faint horizon as plautini. Schmidt chose to assign the pygidia to S1, the very coarse cranidial tuberculation, the absence of plautini rather than to furcifer because one of the pygidia is the third pygidial pleural furrow, and the well developed preserved beneath an incomplete cephalon of plautini. border on the posterior part of the pygidium. Pygidia of However, examination of a plaster replica of this specimen some species of Hoplolichas also resemble Hoplolichoides (CNIGR 36/11101) revealed that the pygidium is not in pygidia in having a very short, broad marginal spine situated enrolled position beneath the cephalon, and consequently immediately behind the second spine, and/or an unpaired there is no reason to conclude that both cephalon and posteromedian spine (e.g. Warburg, 1939, pl. 8, fig. 5; pygidium belong to the same individual as believed by D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 115

Schmidt. In addition, the pygidium is so incomplete (more narrowing at increasing rate to front of bullar lobe; width of so than shown by Schmidt 1885, pl. 2, fig. 17b) that it is not glabella at front of palpebral lobe 140% width across frontal possible to determine whether it belongs to Hoplolichoides lobe and approximately equal to sagittal length (excluding or Hoplolichas. The fragmentary pygidium later assigned to occipital ring) in palpebral view (with palpebral suture furcifer by Schmidt (1907, pl. 2, fig. 9) resembles the horizontal). Occipital ring increasing strongly in length pygidia previously assigned erroneously to plautini. (exsag.) and height adaxially to base of occipital spines; Hoplolichoides conicotuberculatus (NIESZKOWSKI, median part of ring steep and slightly concave (sag.) in front 1859) of spines (Fig. 2.1). Occipital spines stout, diverging back- Fig. 2.1Ð19 wards at about 60¡ proximally, gently curved backwards in 1859 Lichas conico-tuberculata NIESZKOWSKI, p. lateral and dorsal profiles. Large median occipital tubercle 365, pl. 1, figs 7Ð10. present in front of spines, and a pair of slightly smaller 1877 Lichas (Hoplolichas) conico-tuberculata NIESZ- tubercles close to posterior edge of ring behind L1a. Median KOWSKI - Dames, p. 802, pl. 14, figs 2Ð6. part of occipital furrow shallow, transverse medially; lateral 1885 Lichas (Hoplolichas) conicotuberculata NIESZ- part deeply incised and deflected backwards behind L1a. KOWSKI - Schmidt, p. 82, pl. 3, figs 13Ð25. Glabella in front of occipital ring more convex sagittally 1901 Hoplolichas conicotuberculatus (NIESZKOWSKI) than transversely, in palpebral view descending forwards in -Gürich, pl. 20, fig. 14. front of δ-δ and overhanging medial part of anterior border; 1928 Lichas (Hoplolichas) conicotuberculatus NIESZ- longitudinal furrow deepest anteriorly, meeting occipital KOWSKI - Kummerow, p. 36, pl. 2, fig. 5. furrow posteriorly in line (exsag.) with adaxial extremity of 1936 Hoplolichoides conicotuberculatus L1a. L1a with two prominent tubercles situated slightly (NIEZSKOWSKI) - Phleger, p. 602, fig. 23. anteromedially and posterolaterally of centre; furrow in 1937 Hoplolichoides conicotuberculatus (NIESZ- front of L1a collinear with median part of occipital furrow KOWSKI) - Phleger, p. 1087. but shorter (exsag.) and deeper. L1b indistinctly defined by 1939 Hoplolichas conicotuberculatus (NIESZKOWSKI) slight backward deflection of longitudinal furrow and by - Warburg, p. 97, pl. 7, fig. 2. faint transverse depression separating it from bullar lobe 1957 Hoplolichas conicotuberculatus (NIESZKOWSKI) (Fig. 2.6); L1b with large tubercle adaxially. Bullar lobe - Tripp, p. 108, text-fig. 4O; p, 110, text-fig. 5C. widest at midlength in palpebral view, in front of midlength 1958 Hoplolichas conicotuberculatus (NIEZSKOWSKI) partially subdivided adaxially (most distinctly on internal - Tripp, p. 576. moulds) by very narrow (tr.), shallow, transverse S2; posi- 1971 Hoplolichas conicotuberculatus (NIESZKOWSKI) tion of S2 commonly indicated on exterior of exoskeleton - Neben and Krueger, pl. 34, figs 7Ð9. only by weak abaxial deflection and shallowing of longitu- 1988 Hoplolichas conicotuberculatus (NIESZKOWSKI) dinal furrow (Fig. 2.10). Posterior half of median lobe with - Thomas and Holloway, pl. 10, figs 193Ð197. fairly regular arrangement of coarse, paired tubercles in Lectotype Ð Selected by Warburg (1939); cranidium three rows; posterior two rows separated on internal mould figured by Nieszkowski (1859, pl. 1, figs 7, 8), from the by weak transverse depression (S1) in line (exsag.) with front of L1b (Fig. 2.6). Kukruse Stage (C2, lower Caradoc) at Erras (= Erra) or Wannamois (= Vanamõisa), Estonia. The records of the Axial furrow deep, narrow; preglabellar furrow beco- Institute of Geology, Tallinn Technical University, question- ming more sharply impressed adaxially. Anterior border ably identify the lectotype as specimen no. Tr2099 (figured flattened (sag., exsag.), decreasing in length adaxially, its Thomas and Holloway, 1988, pl. 10, fig. 195). That appears margin gently concave in outline abaxially. Fixigenal field unlikely as the specimen does not match Nieszkowki’s steeply declined in front of and behind palpebral lobe (Fig. illustration (e.g. the posterior borders and occipital ring, 2.1), overhanging posterior border adaxially in palpebral excluding the occipital spines, are shown in the illustration view. Posterior border increasing in height and length but are mostly covered by matrix in the specimen). (exsag.) abaxially, its posterior edge curving gently back- Material examined Five cranidia (MB T1809ÐT1811, wards; posterior border furrow deep, curving slightly for- T1814, T1815), two librigenae (MB T1821, T1822) and wards abaxially. Palpebral lobe narrow (tr.), tapering more four pygidia (MB T1812, T1813, T1819, T1820), all from strongly posteriorly than anteriorly, posterior edge situated Kukruse near Jõhvi, Estonia. opposite front of L1b in palpebral view (Fig. 2.6, 10) and Diagnosis – Minimum width of median glabellar lobe slightly farther from sagittal line than anterior edge; palpe- situated level with intersection of axial and palpebral bral furrow strongly curved, shallow at midlength (exsag.); furrows; L1a transverse, ovate. Pygidium with first two palpebral area inflated above level of palpebral lobe (Fig. marginal spines steeply inclined across their width, con- 2.1). Anterior branch of facial suture initially diverging verging backwards; third spine subtriangular. slightly in front of palpebral lobe, thereafter converging Description Ð Glabella approximately equal in width strongly to lateral border furrow, diverging less strongly across occipital ring and L1a, expanding weakly forwards forwards across anterior border; width α-α almost equal to from front of L1a to front of palpebral lobe, thereafter maximum width of glabella. Posterior branch of suture 116 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125

Fig. 2. Hoplolichoides conicotuberculatus (NIESZKOWSKI, 1859), Kukruse Stage (C2, lower Caradoc), Kukruse, Estonia. 1, 5-6 MB T1810, cranidium, figured Dames (1877, pl. 14, fig. 3, 3a); lateral, oblique and palpebral views, × 1.75. 2-3 MB T1809, cranidium, figured Dames (1877, pl. 14, fig. 2); plan and oblique views, × 2. 4, 8, 12-13 MB T1812, pygidium, figured Dames (1877, pl. 14, fig. 5); lateral, oblique, posterodorsal and dorsal views, × 2. 7. MB T1821, librigena, collected Dames 1877; dorsal view, × 2. 9, 14. MB T1822, librigena, collected Dames; dorsal and ventral views, × 2. 10-11 MB T1814, cranidium, collected Dames 1877; palpebral and oblique views, × 1.75. 15-16 MB T1820, pygidium, collected Dames 1876; posterodorsal and dorsal views, × 2. 17. MB T1815, fragmentary cranidium, collected Dames 1876; plan view, × 2. 18-19 MB T1813, pygidium, figured Dames (1877, pl. 14, fig. 6); dorsal view, × 2; marginal spines in dorsolateral view, × 3.

Hoplolichoides conicotuberculatus (NIESZKOWSKI, 1859), Kukruse Stage (C2, Caradoc inférieur), Kukruse, Estonia. 1, 5-6 MB T1810, cranidium, Dames (1877, pl. 14, fig. 3, 3a); vues latérale, oblique et palpébrale, × 1.75. 2-3 MB T1809, cranidium, Dames (1877, pl. 14, fig. 2); vues plane et oblique, × 2. 4, 8,12-13 MB T1812, pygidium, Dames (1877, pl. 14, fig. 5); vues latérale, oblique, postérodorsale et dorsale, × 2. 7. MB T1821, librigena, collecté par Dames 1877; vue dorsale, × 2. 9, 14. MB T1822, librigena, collecté par Dames; vues dorsale et ventrale, × 2. 10-11 MB T1814, cranidium, collecté par Dames 1877; vues palpébrale et oblique, × 1.75. 15-16 MB T1820, pygidium, collecté par Dames 1876; vues postérodorsale et dorsale, × 2. 17. MB T1815, fragment de cranidium, collecté par Dames 1876; vue plane, × 2. 18-19 MB T1813, pygidium, figuré par Dames (1877, pl. 14, fig. 6); vue dorsale, × 2; vue dorsolatérale et épine marginale, × 3. D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 117 curving strongly backwards abaxially, converging back- and interspersed granules; tubercles on occipital spines wards slightly across posterior half of posterior border. point towards distal ends of spines. Coarse tubercles less Librigena with gently convex borders merging with base abundant on librigena than on cranidium. Most of librigenal of long, broad, flattened, sickle-shaped genal spine; lateral doublure with two sets of terrace ridges: a low, widely border expands greatly in width posteriorly, outer margin spaced set running subparallel to inner margin, and an with shallow antennal notch anteromedially. Borders sepa- intervening, very fine, anastomosing set; librigenal margin rated from more convex librigenal field by shallow border and outer part of doublure with coarser, closely spaced, furrows that unite in a uniform curve (Schmidt, 1885, pl. 3, subparallel terrace ridges. Coarse terrace ridges on pygidial fig. 13b, 19); border furrows preserved in MB T1822 but doublure extend onto dorsal surface along (mainly abaxial) most of field missing (Fig. 2.9). Numerous small spines edges of first two spines, where they run oblique to margin present along adaxial edge of genal spine. Librigenal and bear a row of fine granules (Fig. 2.19). doublure broad, its inner edge corresponding approximately Discussion Ð Schmidt (1885) recorded conicotubercula- in position with border furrows. tus in Estonia from the Kukruse Stage (C2) at Kuckers Pygidium with maximum width across base of first (= Kukruse), Erras (= Erra), Wannamois near Tolks (= Van- marginal spine and level with pygidial midlength. Axis amõisa near Kohala), and Kawast (Kavastu near Rakvere), strongly convex (tr.), tapering gently backwards, poorly and from the uppermost part of the underlying Echino- defined posteriorly; transverse row of prominent tubercles sphaerites Limestone (Uhaku Stage, C1c) at Reval situated at change of slope between flattened (sag.) crest of (= Tallinn). From the last locality he illustrated an incom- axis and steeply inclined postaxial region (Fig. 2.4). Articu- plete cephalon with several attached thoracic segments lating half ring short (sag., exsag.), of uniform length over (Schmidt 1885, pl. 3, fig. 13aÐc), the cephalon being most of axial width. First axial ring only slightly longer depicted with a single median occipital spine rather than sagittally than articulating half ring, posterior edge with paired spines. However, the photograph of this specimen weak embayment medially to accommodate poorly defined (Palaeontological Institute, Moscow, no. 4248/121) pro- pseudo-articulating half ring on second axial ring; second vided by Bruton et al. in their internet catalogue of ring longer sagittally than first ring, decreasing slightly in Schmidt’s trilobites (see above), shows that the appearance length laterally; second ring furrow very shallow medially. of a single occipital spine is apparently caused by breakage, First and second rings each with a transverse row of six and that paired spines were probably originally present. tubercles; third ring defined only by alignment of tubercles. Warburg (1939) considered that this specimen may belong Furrow alongside postaxial region collinear with axial to her species Hoplolichoides curvifrons, based on speci- furrow, becoming broad, shallow and poorly defined poste- mens from an erratic of early Caradoc age from Sweden, but riorly at intersection with border furrow. Pleural field the specimen seems to agree in most features with other convex (tr.), steeply downturned abaxially; posterior pleural specimens of conicotuberculatus from Estonia. Outside bands more prominent than anterior bands, extending onto Estonia, conicotuberculatus has been recorded from Swe- border distally. Each posterior band bearing a row of four den (island of Björkön, Uppland), southern Norway, and prominent tubercles; second tubercle (from adaxial end) from glacial erratics in northern Germany (Kummerow, very high and spinose, situated about half way between 1928; Warburg, 1939; Neben and Krueger, 1971). axial and border furrows; most distal tubercle situated on The oldest species of the genus is Hoplolichoides furcifer border. Pleural and interpleural furrows deep on pleural (SCHMIDT, 1885), from the Aseri-Uhaku Stages (C1, field, shallower on border where pleural furrows are de- middle Llanvirn-lowermost Caradoc) of Estonia and Russia flected laterally to reach margin between spines. Posterior (St Petersburg district). It differs from conicotuberculatus in part of pleural field with two or three prominent tubercles having a broader bullar lobe; the minimum width of the arranged in a line directed slightly more strongly backwards median lobe is situated farther back, behind a transverse line than second interpleural furrow. First marginal spine termi- through the intersection of the axial and palpebral furrows; nating just behind transverse line through tip of notch the longitudinal furrow is more strongly curved and is between second and third spines; second spine broader and shallower posteriorly behind S1; and L1a is subtriangular converging more strongly backwards than first, terminating rather than ovate. In the pygidium of furcifer, incorrectly level with tip of posteromedian spine; third spine terminat- assigned to Hoplolichas plautini by Schmidt (1885) (see ing in front of transverse line through tips of second and above), the first two marginal spines are broader than in posteromedian spines; posteromedian spine becoming conicotuberculatus, are less inclined across their width, and rounded in cross section distally. Border wider between do not converge backwards. Hoplolichoides curvifrons third spines than in front of third spines; border furrow (WARBURG, 1939) is most readily distinguishable from shallow behind postaxial region, even shallower where it conicotuberculatus by the third pair of pygidial spines that crosses posterior pleural bands on first two segments. are rounded and lobate rather than subtriangular. Doublure convex. Subfamily PLATYLICHINAE Phleger, 1936 Dorsal surface of cranidium and pygidium with dense Diagnosis – Axial furrow effaced adjacent to L1b, which sculpture of coarse tubercles together with superimposed merges abaxially with fixigenal field. Bullar lobe circum 118 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 scribed, bounded posterolaterally by S1; in some genera, Type species Ð Allolichas longispinus KRUEGER, 1992, bullar lobe expanded backwards to reach or almost reach p. 271, from glacial erratics of the Backsteinkalk (upper L1a, displacing adaxial part of L1b; longitudinal furrow Kukruse Stage, C2 , lower Caradoc) of north-eastern Ger- invariably extends to occipital furrow or L1a. Hypostome many; original designation. with middle body narrower across posterior lobe than across Other species Ð A. crescenticus (REED, 1935) (= Lichas anterior lobe; shoulder situated opposite middle furrow or (Platylichas) vicinus REED, 1935; see Morris 1988,p. posterior lobe of middle body. Pygidium with 2Ð3 pairs of 179); A. glenos (WHITTINGTON, 1962); A. halli (FOER- pleural furrows and three pairs of flattened marginal spines; STE, 1888); A. laxatus (MCCOY, 1846); A. micus (ANTSY- anterior and posterior bands usually flattened. GIN, 1973); A. noctua (PRICE, 1980); A. nodulosus (MC- Genera and subgenera included Ð Platylichas (Platyli- COY, 1851); A. thraivensis (REED, 1935); A.? gracile chas) GÜRICH, 1901; P. (Rontrippia) THOMAS & HOL- (KUMMEROW, 1928); A.? inconsuetus (RAYMOND, LOWAY, 1988; Allolichas KRUEGER, 1992; Autoloxoli- 1925); A.? miseneri (FOERSTE, 1920). chas PHLEGER, 1936; Metalichas REED, 1902. Stratigraphical and geographical range Ð Arenig, Remarks Ð Thomas and Holloway (1988, fig. 362, p. Urals; Caradoc-Ashgill, North America (Indiana, 249) recognized the close affinities between Platylichas and Ohio, ?New York), Ireland, England, Scotland, Wales, Nor- Autoloxolichas, a pair of genera to which Allolichas is also way, Sweden, northern Germany (erratics), Estonia, Arctic related. It is appropriate to use the Subfamily Platylichinae Russia (Vaigach Island and Pai-Khoi). to reflect this grouping, to which we also assign the poorly Diagnosis Ð Platylichine with gently convex (sag., tr.) known Metalichas (see Thomas and Holloway, 1988). This cranidium, glabella not overhanging anteriorly; anterior subfamily was recognised by Hupé (1953) and Balashova border flattened, commonly expanding weakly adaxially, (1960), but Tripp (1957, 1959) and Thomas and Holloway comprising about 10% sagittal cranidial length. Longitudi- (1988) implicitly placed it in synonymy with the Homoli- nal furrow meeting inner end of S1 posteriorly in acute chinae by including Platylichas in the latter subfamily. angle at adaxial extremity of L1a. Long axis of bullar lobe Members of the Platylichinae differ from the Homolichinae almost parallel to sagittal line; minimum width of median in having the axial furrow effaced adjacent to L1b, which lobe situated level with midlength (exsag.) of bullar lobe, consequently is fused with the fixigenal field instead of with less than width of bullar lobe measured across same the bullar lobe to form a composite lobe. The strongly transverse line. Hypostome approximately as wide across oblique furrow bounding the bullar lobe posterolaterally in shoulders as long (sag.), with subcircular middle body. the Platylichinae is not the axial furrow but S1, which meets Pygidium with axis comprising half sagittal length or more; the longitudinal furrow posteriorly and joins the axial three or four axial rings, last ring furrow commonly furrow anteriorly near the front of the palpebral lobe (Fig. incomplete medially; postaxial band narrow. Pleurae with 1.6Ð8). The homology of the glabellar lobes and furrows is three pairs of pleural furrows and three pairs of long and fairly easily determined in Platylichas and Metalichas, slender marginal spines, first two pleural furrows running which have the bullar lobe relatively widely separated from distally onto bases of marginal spines; gently convex border L1a. In Allolichas and Autoloxolichas, however, the bullar present posteriorly, bounded by distinct border furrow lobe has expanded backwards to reach or almost reach L1a, joining furrow alongside postaxial band with last pleural thus assuming more of the appearance of the composite and interpleural furrows. lateral lobe of the Homolichinae. In some specimens of Remarks Ð Krueger (1992) included in Allolichas only Allolichas and Autoloxolichas the axial furrow is weakly the type species, A. longispinus, the long median occipital discernible adjacent to L1b, running almost parallel with the spine of which he considered to be the most important sagittal axis, showing that the enlarged bullar lobe in these diagnostic character of the genus. In other characters, such genera has displaced L1b, which is very small and subtri- as the intersection of the longitudinal furrow and S1 in an angular in outline. Given the similarities in gross glabellar acute angle at the adaxial extremity of L1a, the narrowness morphology shared by Platylichas and the lichakephalid of the median lobe between the bullar lobes, the weakly Lichakephalus, the Platylichinae appear less derived in their adaxially expanding anterior border, the long (sag.) pygidial glabellar structure than the Homolichinae. axis and narrow postaxial band, the long and slender Thomas and Holloway (1988) regarded the hypostomal pygidial marginal spines, and the gently convex border on characters as important in characterizing their concept of a the posterior part of the pygidium, longispinus resembles united Homolichinae + Platylichinae, but those shared simi- species such as ‘Lichas’ laxatus MCCOY, 1846 (see Dean, larities are now regarded as primitive for lichids as a whole 1963, p. 235, pl. 43, figs 1Ð2, 5, 8Ð12), ‘Trochurus’ (see remarks on Homolichinae). Not all platylichine hypos- nodulosus MCCOY, 1851 (see Thomas and Holloway, tomes retain the primitive condition of being longer than 1988, pl. 9, figs 185, 188Ð192), and ‘Platylichas’ noctua wide, some being more elongated (e.g. Allolichas, see PRICE, 1980. Such species, which were included in Au- below; some species of Platylichas, see Thomas and Hol- toloxolichas by Thomas and Holloway (1988), lack the long loway, 1988, pp. 184, 213, pl. 9, fig. 173). occipital spine of longispinus, though a small median spine Genus Allolichas KRUEGER, 1992 or tubercle may be present (e.g. Warburg, 1939, pl. 12, fig. D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 119

8a; Thomas and Holloway, 1988, pl. 9, figs 188Ð190). Fig. 3.1Ð10 However, we do not consider the presence of cranidial 1885 Lichas St. Mathiae SCHMIDT, p. 115, pl. 5, figs spines to be especially important taxonomically in Lichida 11Ð16. (Thomas and Holloway, 1988). We therefore expand the 1936 Autoloxolichas st.-mathiae (SCHMIDT) - Phleger, concept of Allolichas to include all the species that we fig. 78. previously assigned to Autoloxolichas, except for the type 1937 Platylichas st. mathiae FR. SCHMIDT - Öpik, p. species of the latter. See the discussion of Autoloxolichas for 57, pl. 22, fig. 2, text-fig. 15. comparison of that genus with Allolichas. 1957 Platylichas sanctaemathiasae (SCHMIDT) - Tripp, The hypostome of Allolichas is distinctive in its rather p. 116. elongated outline and subcircular middle body (see Whit- 1958 Platylichas sanctaemathiasae (SCHMIDT, 1885) - tington, 1962, pl. 7, figs 9, 10; Dean, 1963, pl. 43, fig. 12; Tripp, p. 576. Price, 1980, pl. 113, fig. 2; Krueger, 1992, pl. 1, fig. 3). 1988 Autoloxolichas sanctamathiae (SCHMIDT, 1885) - Genus Autoloxolichas PHLEGER, 1936 Thomas and Holloway, p. 206, pl. 10, figs 212, 213. Type species ÐLichas St. Mathiae SCHMIDT, 1885,p. in press Autoloxolichas sanctamathiae (SCHMIDT, 115, from the Jõhvi (D1) and Keila (D2) stages (middleÐup- 1885) - Whittington, fig. 4.1Ð4.5. per Caradoc) of Estonia; original designation. Type material Ð Lectotype designated herein, cranidium Other species Ð None known. CNIGR 92/11101, figured Schmidt (1885, pl. 5, fig. 13),

Diagnosis Ð Platylichine with gently convex (sag., ex- Fig. 3.6 herein; from the Keila (D2) stage (middleÐupper sag., tr.) cranidium; anterior border short (less than half Caradoc) of Kegel (= Keila), Estonia. This designation is sagittal length of occipital ring), upper surface sloping made in order to clarify the application of the species name, forward at almost same angle as front of glabella, anterior as the pygidia associated with the cranidia by Schmidt surface vertical. Bullar lobe ovate in outline, circumscribed (1885) may not be conspecific. Paralectotypes include by axial and longitudinal furrows and S1, separated from cranidia CNIGR 90/11101 (figured Schmidt, 1885, pl. 5, fig. L1a posteriorly by very short (exsag.), slightly depressed 11; Fig. 3.5 herein) and CNIGR 91/11101 (Schmidt, 1885, region; long axis of bullar lobe oriented at about 30¡ to pl. 5, fig. 12; Fig. 3.8 herein); hypostome CNIGR 93/11101 sagittal line Minimum width of median lobe situated well (Schmidt, 1885, pl. 5, fig. 14; Fig. 3.4 herein); and pygidia behind midlength (exsag.) of bullar lobe, less than width of CNIGR 94/11101 (Schmidt, 1885, pl. 5, fig. 15a, b; Fig. 3.9 bullar lobe measured across same transverse line. herein) and CNIGR 95/11101 (Schmidt 1885, pl. 5, fig. 16; Cranidium with sculpture of dense granules grading into Fig. 3.7, 10 herein). Additional syntypes mentioned by terrace ridges on front of glabella. Schmidt (1885) but not figured by him have not been traced. Remarks Ð Öpik (1937) considered that the pygidia Other material Ð Cranidia GIE Tr2254 (figured Öpik assigned to sanctamathiae by Schmidt are not conspecific 1937, pl. 22, fig. 2; Thomas and Holloway, 1988, pl. 10, fig. with the cranidia. Sculptural differences (granules grading 212), GIE Tr19546 (figured Thomas and Holloway, 1988, anteriorly into undulating ridges on the cranidia; zigzag pl. 10, fig. 213), and RM Ar54838aÐb (Fig. 3.1Ð3). scaly ridges on the pygidium) lend some support to this Description Ð Cranidium approximately twice as wide at view. Because of the uncertainty in the assignment of the posterior margin as long (sag.); glabella widest across bullar pygidia, the generic diagnosis is based on cranidial charac- lobes (level with intersection of axial and palpebral furrows) ters alone. and occipital ring, slightly narrower across frontal lobe and Autoloxolichas is here restricted to the type species, the L1a, narrowest across L1b (level with posterior end of other species included in the genus by Thomas and Hollo- bullar lobe; see below). Occipital ring with small, weak way (1988) being placed in Allolichas. Allolichas is very median swelling close to posterior margin. L1a, bullar and similar to Autoloxolichas in the development of the frontomedian lobes with slight independent convexity. L1a cranidial lobes and furrows but differs in having the lenticular, almost as wide (tr.) as median part of occipital longitudinal furrow extending farther posteriorly, reaching furrow. L1b generally not defined abaxially, but in some the adaxial extremity of L1a instead of uniting with the specimens (e.g. Thomas and Holloway, 1988, pl. 10, fig. inner end of S1 a short distance in front of L1a; the bullar 213, left side) axial furrow faintly visible in front of L1a, lobe is acute posteriorly rather than rounded, and is less running almost parallel to sagittal line from a point level obliquely oriented, its long axis lying approximately parallel with 33% distance between abaxial and adaxial extremities to the sagittal line; the minimum width of the median lobe of L1a, meeting outer end of S1 just behind intersection of is situated farther forwards, level with the midlength (ex- axial and palpebral furrows. S1 directed posteromedially at sag.) of the bullar lobe; and the anterior border is horizontal about 40¡ to sagittal line, not clearly differentiated in depth rather than sloping forwards, and commonly lengthens or course from axial furrow immediately in front of S1, slightly medially. Pygidia of Allolichas are not similar to shallowing posteriorly towards junction with longitudinal those assigned to Autoloxolichas sanctamathiae by Schmidt furrow. Bullar lobe ovoid, more pointed posteriorly than (1885). anteriorly. Longitudinal furrow meeting axial furrow at Autoloxolichas sanctamathiae (SCHMIDT, 1885) about 25% glabellar length (sag.), directed slightly forwards 120 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125

Fig. 3. Autoloxolichas sanctamathiae (SCHMIDT, 1885), Keila Stage (D2, middle-upper Caradoc), Estonia. 1-3. RM Ar54838a, exfoliated cranidium, collected V. Jaanusson 1941; dorsal, oblique and lateral views, × 2.25; Pääsküla. 4 CNIGR 93/11101, mostly exfoliated hypostome, figured Schmidt (1885, pl. 5, fig. 14); ventral view, × 2; St Mathias (= Madise). 5. CNIGR 90/11101, partly exfoliated cranidium, figured Schmidt (1885, pl. 5, fig. 11); dorsal view, × 1.75; Madise. 6. CNIGR 92/11101, cranidium, lectotype, figured Schmidt (1885, pl. 5, fig. 13a, b); dorsal view, × 3; Keila. 7, 10. CNIGR 95/11101, exfoliated pygidium, figured Schmidt (1885, pl. 5, fig. 16); posterior and dorsal views, × 1.75; Haljal (= Haljala) or Friedrichshof (= Saue). 8. CNIGR 91/11101, cranidium, figured Schmidt (1885, pl. 5, fig. 12); dorsal view, × 4; Spitham (= Põõsaspea). 9. CNIGR 94/11101, partly exfoliated pygidium, figured Schmidt (1885, pl. 5, fig. 15a, b); dorsal view, × 3.5; Madise. All photographs except Fig. 6 are of plaster replicas.

Autoloxolichas sanctamathiae (SCHMIDT, 1885), Keila Stage (D2, Caradoc moyen-supérieur), Estonia. 1-3. RM Ar54838a, cranidium esfolié, collecté par V. Jaanusson 1941; vues dorsale, oblique et latérale, × 2.25; Pääsküla. 4 CNIGR 93/11101, hypostome presque entièrement exfolié, figuré par Schmidt (1885, pl. 5, fig. 14); vue ventrale, × 2; St Mathias (= Madise). 5. CNIGR 90/11101, cranidium partiellement exfolié, figuré par Schmidt (1885, pl. 5, fig. 11); vue dorsale, × 1.75; Madise. 6. CNIGR 92/11101, cranidium, lectotype, figuré par Schmidt (1885, pl. 5, fig. 13a, b); vue dorsale, × 3; Keila. 7, 10. CNIGR 95/11101, pygidium exfolié, figuré par Schmidt (1885, pl. 5, fig. 16); vues postérieure et dorsale, x 1.75; Haljal (= Haljala) ou Friedrichshof (= Saue). 8. CNIGR 91/11101, cranidium, figuré par Schmidt (1885, pl. 5, fig. 12); vue dorsale, × 4; Spitham (= Põõsaspea). 9. CNIGR 94/11101 pygidium partiellement exfolié, figuré par Schmidt (1885, pl. 5, fig. 15a, b); vue dorsale, × 3.5; Madise. before curving backwards in a broad arc to join S1; axial and preglabellar furrows. Posterior border weakly narrowest part of median lobe situated at about 60% convex (exsag.), expanding strongly abaxially; posterior glabellar length (sag.) from anterior. Palpebral lobe situated border furrow directed obliquely forwards abaxially. Ante- less than its own length from posterior cranidial margin, rior border of uniform length (sag., exsag.). approximately sloping abaxially almost at same angle as fixigena, lying 50% sagittal length of occipital ring; anterior border furrow farther from sagittal line posteriorly than anteriorly, poste- much weaker on external surface than on internal mould. rior edge opposite posterior edge of bullar lobe; palpebral Cranidium with sculpture of dense granules of two sizes, on furrow much more weakly curved than palpebral margin, larger specimens merging into undulating transverse ridges meeting axial furrow level with cranidial midlength (sag.). on frontal lobe of glabella. Posterior branch of facial suture sigmoidal, diverging Hypostome with sagittal length 80% width across shoul- strongly backwards; anterior branch running parallel to ders, latter situated just behind midlength (sag.). Middle D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 121 body gently convex transversely and weakly convex sagit- or les stransversely; doublure with widely spaced, continu- tally; anterior lobe comprising about 75% sagittal length of ous terrace ridges concentric with margins. middle body, subelliptical in outline, widest at midlength Remarks Ð The smallest cranidium, CNIGR 91/11101 (sag.); middle furrow situated opposite shoulder, deep, (Fig. 3.8), differs from the larger ones in lacking any trace transverse, abruptly dying out about half way between of transverse ridges on the front of the glabella, all pre- lateral border furrow and sagittal line; posterior lobe 70% served areas of exoskeleton (which include part, but not the maximum width of anterior lobe, with elongated maculae anteriormost part, of the frontal lobe) having a dense extending posteromedially from middle furrow. Lateral sculpture of granules of two sizes. On the large cranidium border convex (tr.) behind shoulder, outer edge with slight RM Ar54838a-b the exoskeleton adheres to the external embayment opposite posterior border furrow; lateral border mould so that the exterior surface is not visible, but the furrow shallower and broader opposite posterior lobe of internal mould shows traces of the undulating, transverse middle body than opposite anterior lobe, even shallower ridges on the frontal lobe (Fig. 3.1Ð3) The illustration of the behind intersection with posterior border furrow, where it is largest cranidium, CNIGR 90/11101, given by Schmidt deflected outwards slightly before curving inwards and (1885, pl. 5, fig. 11) shows transverse ridges on the fragment dying out. Posterior border slightly convex (sag., exsag.), of exoskeleton adhering to the frontal lobe, but no trace of highest anteriorly, posterior margin with broad, rounded sculpture now remains on the specimen itself, the surface of median embayment; posterior border furrow deep. Adhering the exoskeletal fragment having been obliterated by scra- fragment of exoskeleton with terrace ridges on anterior ping. This specimen is also less complete on the left side wing and around margin of shoulder, and with weak pits on than shown in Schmidt’s illustration, most of the fixigena, border opposite shoulder; internal mould with weak the anterior border, and the lateral part of the occipital ring wrinkles on outer part of lateral border posteriorly, replaced being missing. These differences may be due to restoration by shallow dimples (swellings on interior of exoskeleton) in the illustration or to later damage to the specimen. adaxially on lateral and posterior borders. Subfamily TROCHURINAE Phleger, 1936 Pygidium (specimens possibly incorrectly assigned to this species) with maximum width situated well in front of Genus Akantharges PHLEGER, 1936 midlength (sag.) and level with posterior end of axis. Axis Type species Ð Lichas Gourdoni BARROIS, 1886,p. conical, approximately 40% maximum pygidial width ante- 126, from the Eifelian of the central Pyrenees, France; riorly, poorly defined posteriorly; in transverse profile, axis original designation. strongly convex with maximum curvature along sagittal line, in lateral profile gradually decreasing in height poste- Other species Ð A. erbeni (MEISCHNER, 1965); A. sp. riorly over most of its length but subsiding more abruptly of Thomas and Holloway (1988). behind transverse line through adaxial ends of second Stratigraphical and geographical range Ð Middle De- interpleural furrows. First axial ring with slight relief, vonian (EifelianÐGivetian); France (Pyrenees), Germany longest (sag., exsag.) distally and midway between axial (Rheinisches Schiefergebirge), Morocco. furrow and sagittal line, defined by continuous ring furrow; second ring much weaker, ring furrow dying out medially; Diagnosis Ð Trochurine with strongly convex (sag., ex- very faint trace of third ring furrow present abaxially on sag.) glabella not overhanging anterior border; longitudinal larger pygidium. Pleurae weakly convex (tr.), sloping gently furrow very shallow anteriorly and behind S1; L1 depressed abaxially; lateral margin curving strongly adaxially from medially; L1a not defined. Palpebral lobe small, situated region of maximum pygidial width to tip of first marginal low on cheek rather far from glabella; anterior and posterior spine. First spine very short, broad, separated from second sections of facial suture collinear. Posterolateral cranidial spine by narrow incision; shape of second and third (if lobe bearing long (exsag.) ridge curving forwards and present) spines unknown. First two pleural furrows not backwards abaxially, and bounded posteriorly by distinct running onto marginal spines distally but meeting outer end furrow; ridge may interrupt posterior border furrow distally. of succeeding interpleural furrow at pygidial margin be- Subgenal notch may be well developed; genal spine long tween spines; first pleural furrow more strongly curved than and blade-like. Pygidium with three pairs of long, slender second; third pleural furrow not impressed. First interpleural marginal spines that are rounded in cross-section. Axis furrow weakly concave backwards, almost straight; second comprising 66% sagittal length of pygidium or more, with convex backward. Postaxial band funnel-shaped, narrowing one or two prominent axial rings and at least eight addi- backwards more strongly in front of transverse line through tional, poorly defined rings; postaxial ridge indistinct or distal ends of first pleural and interpleural furrows than absent. Anterior pleural bands slightly inflated on segments behind this line. Doublure very wide, extending forwards in 1Ð3, on third segment running subparallel with sagittal axis sagittal line to posterior end of axis, having shallow radial anteriorly and converging posteriorly; pleural and interpleu- furrows abaxially beneath pleural furrows. Dorsal surface of ral furrows shallow; border absent. pygidium with scaly sculpture, on pleurae having appea- Remarks Ð A distinctive feature of Akantharges is the rance of discontinuous, serrated terrace ridges aligned more rounded (exsag.) ridge curving forwards and backwards 122 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 abaxially across the posterolateral cranidial lobe. This ridge, Akantharges erbeni (MEISCHNER, 1965) which bears a number of large tubercles, is bounded Fig. 4.1Ð14 posteriorly by a rather sharp furrow originating near the outer end of the occipital furrow and curving forwards 1965 Acanthopyge erbeni MEISCHNER, p. 124, pl. 1, initially and then backwards abaxially towards the posterior figs 1Ð7, text–figs 1Ð6. border furrow. The ridge and furrow are well developed in 1998 Akantharges? cf. erbeni (MEISCHNER, 1965) - the type species, A. gourdoni, and in the unnamed species Basse, pl. 15, fig. 26aÐb. from Morocco (see Thomas and Holloway, 1988, pl. 14, figs ?1998 Akantharges?gr.erbeni (MEISCHNER, 1965) - 300, 303, 305), but they are weaker in A. erbeni (see Basse, Basse, p. 78, pl. 11, fig. 8. 1998, pl. 15, fig. 26aÐb; Fig. 4.6, 8, 10Ð11 herein). A similar ridge and furrow are present also in Ceratarges, as noted by Holotype - Internal and external moulds of cranidium Gö Thomas and Holloway (1988), but are not known in other 548Ð1; figured Meischner (1965, pl. 1, fig. 1aÐc), Fig. lichids. In Ceratarges the ridge carries the eye (situated at 4.1Ð2, 5 herein; from Givetian phyllites near Gellershausen, the end of a long stalk) and, lateral to the base of the eye Kellerwald, Germany. stalk, the posterior branch of the facial suture, but in Diagnosis Ð L1 shorter (sag.) than occipital ring; median Akantharges the eye and the posterior branch of the facial and bullar lobes without paired arrangement of coarse suture have migrated laterally so that they are no longer tubercles; curved ridge on posterolateral cranidial lobe situated on the ridge. relatively weak, not interrupting posterior border furrow The relationships of many genus-group taxa within the distally; subgenal notch well developed. Trochurinae are unclear. This is particularly so for the Remarks Ð Meischner (1965) gave an exhaustive de- Devonian forms, which are commonly both distinctive and scription of A. erbeni, as well as providing reconstructions imperfectly known. Based on glabellar and pygidial fea- of the cephalon and pygidium. The specimens have all been tures, and on the supposed absence from both of a subgenal flattened tectonically to some extent, and some have also notch, Thomas and Holloway (1988, p. 252, fig. 365) been sheared, affecting the convexity of the exoskeleton to tentatively suggested that Akantharges might have been varying degrees. From examination of a range of specimens derived from Richterarges. It is now known that a subgenal it is apparent that Meischner’s (1965, fig. 2e) depiction of notch may be present in Akantharges. Thomas and Hollo- the bullar and posterolateral cranidial lobes as subconical, way also suggested a possible derivation of Ceratarges, and posterolaterally curving projections represents an artefact of other genera with deep subgenal notches and medially deformation rather than the original appearance of these shortened L1, from Acanthopyge (Lobopyge). lobes. These lobes were probably originally evenly rounded Adrain (1994) adopted a restricted definition of the (exsag.). related Richterarges, assigning some species formerly ac- Comparison with A. gourdoni is hindered by the strong commodated there to his Borealarges. He (p. 1084) reco- deformation of the material of that species, but obvious gnised a Richterarges/Borealarges/Terranovia clade within differences from A. erbeni include: L1 is longer (sagittal the Trochurinae but, in discussion, identified no particular length greater than that of the occipital ring); the curved points of similarity suggesting a close relationship between ridge on the posterolateral cranidial lobe is more distinct Ceratarges and this clade. The common possession of the and interrupts the posterior border furrow distally; the curved ridge and furrow on the posterolateral cranidial lobe subgenal notch is much shallower; and the pygidial axis is may indicate that Akantharges and Ceratarges are closely longer (about 85% of the sagittal length of the pygidium). related, and were derived from a common ancestor. The well preserved cranidium of Akantharges sp. from The pygidium of A. gourdoni is not well known due to Morocco (Thomas and Holloway, 1988, pl. 14, figs deformation of the specimens, and consequently Thomas 299Ð300, 303) differs from A. erbeni in that L1 is longer and Holloway (1988) did not include pygidial characters in (sag.); the curved ridge on the posterolateral cranidial lobe their generic diagnosis. Pygidial characters in the revised is more distinct and interrupts the posterior border furrow diagnosis given above are based mainly on the somewhat distally; the subgenal notch is non-existent; there are promi- better preserved specimens of A. erbeni. In overall propor- nent paired tubercles on the median glabellar and bullar tions, and in the three pairs of long, slender marginal spines lobes; and there are three very coarse tubercles in a row on that are rounded in cross section, the pygidium of the curved ridge on the posterolateral cranidial lobe. Akantharges resembles that of Acanthopyge (Acanthopyge), The cranidium from Usseln, Germany, figured by Basse but the latter is distinguished mainly by the presence of a (1998, pl. 15, fig. 26aÐb) as Akantharges? cf. erbeni agrees distinct postaxial band bordered laterally by furrows. If the with the types in all observable characters and is undoub- above suggestion of a common ancestry for Akantharges tedly conspecific, but worthwhile comparisons cannot be and Ceratarges is correct, then A. (Acanthopyge) is less made with the incomplete pygidium figured by Basse (1998, closely related to Akantharges. pl. 11, fig. 8) as Akantharges?gr.erbeni. D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125 123

Fig. 4. Akantharges erbeni (MEISCHNER, 1965), Givetian phyllites near Gellershausen, Kellerwald, Germany. 1-2, 5. Gö548-1 cranidium, holotype, figured Meischner (1965, pl. 1, fig. 1aÐc); latex cast of external mould, dorsal view, and internal mould, dorsal and oblique views, × 3.25. 3, 11. Gö548-69 cranidium; latex cast of external mould and internal mould, dorsal views × 3.25. 4. Gö548-7 librigena; latex cast of external mould, ventral view, × 3.5. 6. Gö548-137 cranidium; latex cast of external mould, dorsal view, × 3.25. 7. Gö548-237 hypostome; latex cast of external mould, ventral view, × 4.5. 8. Gö548-76 cranidium; latex cast of external mould, × 3. 9. Gö548-134 cranidium; latex cast of external mould, dorsal view, × 3. 10. Gö548-24 cranidium; latex cast of external mould, dorsal view, × 3.25. 12. Gö548-12 pygidium, figured Meischner (1965, pl. 1, fig. 6; left and right reversed in photograph); natural mould, dorsal view, × 2. 13. Gö548-74, pygidium; latex cast of external mould, dorsal view, × 1.75. 14. Gö548-278 pygidium; latex cast of natural mould, ventral view, × 2. Akantharges erbeni (MEISCHNER 1965), phyllites du Givétien près de Gellershausen, Kellerwald, Germany. 1-2, 5. Gö548-1 cranidium, holotype, figuré par Meischner(1965, pl. 1, fig. 1aÐc); moulage en latex d’un moule externe, vue dorsale et moule interne, vues dorsale et oblique, × 3.25. 3, 11. Gö548-69 cranidium; moulage en latex d’un moule externe et d’un moule interne, vue dorsale, × 3.25. 4. Gö548-7 librigena; moulage en latex d’un moule externe, vue dorsale, × 3.5. 6. Gö548-137 cranidium; moulage en latex d’un moule externe, vue ventrale, × 3.25. 7. Gö548-237 hypostome; moulage en latex d’un moule externe, vue ventrale, × 4.5. 8. Gö548-76 cranidium; moulage en latex d’un moule externe, × 3. 9. Gö548-134 cranidium; moulage en latex d’un moule externe, vue dorsale, × 3. 10. Gö548-24 cranidium; moulage en latex d’un moule externe, vue dorsale, × 3.25. 12. Gö548-12 pygidium, figuré par Meischner(1965, pl. 1, fig. 6; photographies gauche et droite inversées); moule naturel, vue dorsale, × 2. 13. Gö548-74 pygidium; moulage en latex d’un moule externe, vue dorsale, × 1.75. 14. Gö548-278 pygidium; moulage en latex d’un moule naturel, vue ventrale, × 2. 124 D.J. Holloway, A.T. Thomas / Geobios 35 (2002) 111–125

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