Atti Soc. it. Sci, nat. Museo civ. Stor. nat. Milano, 143/2002 (I): 105-115, Luglio 2002 Silvia Brambilla*, Alessandro Garassino*, Giovanni Pasini** & Giorgio Teruzzi* Studies on Permo-Trias of Madagascar. 6. First record of Cycloidea from thè Lower Triassic (Olenekian) of Ambilobé region (NW Madagascar) Abstract - We describe a small sample of cycloids, discovered in some outcrops from thè Lower Triassic (Olenekian), located in Ambilobé region (NW Madagascar). Two new species are here described, Cyclus maclagascariensis n. sp. and Halicyne gondwanae n. sp. (order Cycloidea Glaessner, 1928. family Cyclidae Packard, 1885). It is thè first report of this type of crustaceans in thè Gondwana. In fact, all previous specimens were collected in outcrops located in Laurasia (N America and Europe). Key words: Crustacea, Cycloidea, Lower Triassic. NW Madagascar. Riassunto - Studi sul Permotrias del Madagascar. 6. Prima segnalazione di ciclidi nel Triassico inferiore (Olenekiano) della regione di Ambilobé (NO Madagascar). Viene descritto un piccolo campione di crostacei cicloidei, rinvenuti in alcuni affioramenti del Triassico inferiore (Olenekiano), localizzati nella regione di Ambilobé (NO Madagascar). Lo studio di questo campione ha portato alla descrizione di Cyclus madagascariensis n. sp. e di Halicyne gondwanae n. sp. (Ordine Cycloidea Glaessner, 1928, famiglia Cyclidae Packard, 1885). Il riveni- mento di crostacei cicloidei in Madagascar rappresenta una importante scoperta in quanto trattasi della prima segnalazione di questo gruppo di crostacei nel Gondwana; finora gli unici rinvenimen¬ ti erano limitati a giacimenti localizzati nel Laurasia (Nord America e Europa). Parole chiave: Crustacea, Cycloidea, Triassico inferiore, NO Madagascar. Introduction The fossiliferous levels of thè Lower Triassic marine sediments located S-SW of thè village of Ambilobé (Fig. 1), about 150 km SW of Diego Suarez (Antsiranana) are known sirice thè beginning of last century (Besairie, 1932). This paper deals with thè description of cycloid crustaceans from thè Lower Triassic of thè Ambilobé region (NW Madagascar), increasing not only our * Museo Civico di Storia Naturale, C.so Venezia 55, 20121 Milano, Italia, e-mail: a.garassi- [email protected]; [email protected] ** Museo Civico dei Fossili di Besano, Via Prestini 5, 21050 Besano (Varese), Italia, e-mail: fos¬ si [email protected] 1 06 SILVIA BRAMBILLA, ALESSANDRO GARASSINO, GIOVANNI PASINI & GIORGIO TER UZZI Fig. 1 - Geographical map of NW Madagascar. The arrow indicates Mahatsara outcrop where thè study specimens were discovered. Fig. 1 - Mappa geografica del NO Madagascar. La freccia indica il giacimento di Mahatsara dove gli esemplari studiati sono stati rinvenuti. STUDIES ON PERMO-TRIAS OF MADAGASCAR 1 07 knowledge about this group of crustaceans, but representing thè first record of cycloids in Gondwana. The famous faunal assemblage of Ambilobé region, comprising invertebrates (ammonites, nautiloids, bivalves, annelids, limulids, crustaceans, like as decapods, thylacocephalans and conchostracans, and vertebrates (many fishes and rare amphibians), was thè subject of many studies during thè last century and at thè beginning of this new century (for thè references see Garassino and Pasini, 2002). The present research is part of a program of studies started in thè eighties of thè last century by thè Department of thè Invertebrate Palaeontology of Museo Civico di Storia Naturale di Milano on thè sample of its own collection of thè Lower Triassic fossils of thè Ambilobé region. This research program was car- ried out by thè co-operation and thè help of thè late Dr. Jeannot Rasoanaivo, Director of Geological Service of Madagascar. Previous studies of cycloids Cycloid crustaceans are very rare in thè fossil record and their morphological features are not well known because of their poor state of preservation. Cycloid crustaceans were described for thè first tinte by Phillips (1835) who, studying one specimen discovered in thè Carboniferous of Yorkshire, ascribed it to Agnostus radialis, a trilobite. De Koninck (1841) concluded that Phillips’ spec¬ imen was not a trilobite and described thè genus Cyclus, for this specimen and for other samples from thè Carboniferous of Belgium. Von Meyer (1838) reported a new species from thè Muschelkalk, ascribing it to Limulus agnotus. Subsequently, von Meyer (1844) realised that thè specimen previously ascribed to Xifosura, was not a limulid and so erected thè new genus Halicyne, without pointing out its sys- tematic position. Von Meyer (1847) described another specimen from thè sante beds, ascribing it to thè sante genus Halicyne von Meyer, 1844, but ascribing it to another species. So in thè first part of thè nineteenth century two genera of cycloid crustaceans were recognised: Cyclus de Koninck, 1841, and Halicyne von Meyer, 1844. Von Seebach (1857) collected three poorly preserved specimens from thè Triassic of Thuringia, ascribing them to Halicyne von Meyer, 1844. Schafhautl (1863) ascribed a form from thè Triassic of Alps to Carcinaspis pustulosus, even though thè morphological features of this specimens resentbled Halicyne von Meyer, 1844. Woodward (1868, 1870, 1893, 1894) described cycloids in great numbers, ascribing five species from thè Carboniferous of thè British Isles to Cyclus de Koninck, 1841, while Peach (1883) ascribed another species to Cyclus de Koninck, 1841 front thè Coal Measures of Scotland and Reed (1893) described a new species of Cyclus de Koninck, 1841 from thè Carboniferous Liniestone of thè neighbourhood of Settle (Great Britain). In parallel with these studies, von Schauroth (1854) reported a small granulate shell, Hemitrochiscus paradoxus, from thè Upper Permian of Germany, while Gemmellaro (1890) described from thè Permian of Sicily (Italy) Oonocarcinus insignis, and Stolley (1915) reported thè two species, Cyclocarcinus serratus and Mesoprosopon traisinum front thè Triassic of thè Alps and thè Balkans. Packard (1885, 1886) described thè first American species of Cyclus de Koninck, 1841 from thè Pennsylvanian (Upper Carboniferous) deposits of Mazon Creek (Illinois). Rogers (1902) described some new forms from thè Pennsylvanian limestone of Missouri, ascribing them to Cyclus de Koninck. 1841. Woodward (1905) pointed out some new morphologi- 1 08 SILVIA BRAMBILLA, ALESSANDRO GARASS1NO, GIOVANNI PASINI & GIORGIO TERUZZI cal features ot two species previously described in 1868 and 1870. Reed (1908) described a new species of Cyclus de Koninck, 1841 from thè Carboniferous Limestone ot Ireland. Bill (1914) reported specimens of Halicyne von Meyer, 1844 troni thè Buntsandstein (France), while Trauth (1918) described Halicyne von Meyer, 1844 from thè Upper Triassic of Alps. Triimpy ( 1957) erected a new species of Halicyne from thè Muschelkalk of Wutachtal (Baden, Germany), Kramarenko (1961) extended thè geographic range of Cyclus de Koninck, 1841 when he described a new species from thè Lower Permian of Urals, and Goldring (1967) introduced a new species of Cyclus de Koninck, 1841 from thè Upper Viséan (Lower Carboniferous) of England. Gali and Grauvogel ( 1967) added sig- nificantly to thè knowledge ot Halicyne von Meyer, 1844 and thè Cycloidea Glaessner, 1928, but leaving some doubts on thè morphology and affinities of Halicyne von Meyer, 1844. Glaessner (1969) provided a summary review of thè cycloids, even though their status within thè Crustacea remained uncertain. Zorn (1971) reported thè presence ot three species of Halicyne von Meyer, 1844 and an undescribed specimen ot cycloid from thè Ladinian (Middle Triassic) of Alps. Clark ( 1989) conducted thè most recent study of Cyclus de Koninck, 1841 based on sample from thè Namurian (Lower Carboniferous) shales of Scotland. Recently, Schram et al. (1997) ascribed thè Cycloidea Glaessner, 1928 to Maxillopoda Dahl, 1956, recognising three families: Cyclidae Packard, 1885 with Cyclus de Koninck, 1841, Halicyne von Meyer, 1844, Apionicon Schram et al., 1997 and Carcinaspid.es Glaessner, 1969 (nom. subst. prò Carcinaspis Schafhàutl, 1863); Hemithrochiscidae Trauth, 1918 with Cyclocarcinides Glaessner, 1969 (nom. subst. prò Cyclocarcinus Stolley, 1914), Oonocarcinus Gemmellaro, 1880 and Hemitrochiscus Schauroth, 1854; Mesoprosopidae Glaessner, 1928 with Mesoprosopon Stolley, 1914. Material The present study is based on five specimens, discovered in different out- crops around Ambilobé, along Ifasy river and in particular near Mahatsara vil- lage. The specimens are preserved more or less flattened inside subellipsoidal nodules. Their study allowed thè description of Cyclus madagascariensis n. sp. (two specimens) and Halicyne gondwanae n. sp. (three specimens). The cycloids are associated with decapod crustaceans (MSNM Ì25461, Ì22868) and fishes, like as Austrolosomus (MSNM Ì25460). Acronym: MSNM: Museo Civico di Storia Naturale di Milano. Systematic Palaeontology Class Maxillopoda Dahl, 1956 Subclass Halicyna Gali and Grauvogel, 1967 Order Cycloidea Glaessner, 1928 Family Cyclidae Packard, 1885 Genus Cyclus de Koninck, 1841 Type species: Agnostus radialis Phillips, 1835 109 STUDIES ON PERMO-TRIAS OF MADAGASCAR Fig. 2 - The new erosion. locateci at south of Mahatsara village, where thè holotype of Cyclus mada- gascariensis n. sp. was discovered. Fig. 2 - La nuova erosione, localizzala a sud del villaggio di Mahatsara, dove Folotipo di Cyclus madagascariensis n. sp. è stato rinvenuto. 1 1 0 SILVIA BRAMBILLA, ALESSANDRO GARASS1NO. GIOVANNI PASINI & GIORGIO TERUZZI Cyclus madagascariensis n. sp. Fig. 2 Diagnosti: carapace subcircular; dorsal surface of carapace slightly papillose; thin longitudinal ridge in mediali and posterior half of dorsal surface of carapace; antennules and antennae attached laterally to frontal extension; postero-lateral margins of carapace smooth. Etymology; thè trivial name refers to Madagascar, where thè specimens were discovered. Holotype: MSNM Ì25462. Paratype: MSNM Ì25460. Type locality: area south of Mahatsara (Ifasy river); thè holotype comes from a new erosion, located at south of Mahatsara village, from thè holotype was col- lected recently in thè outcrop by one of thè authors (G. Pasini). GeologicaI cige: Olenekian (Lower Triassic). Occurrence and measurements: we ascribe to this species two specimens (MSNM Ì25460, Ì25462). MSNM Ì25460: carapace length = 0.8 cm MSNM Ì25462: carapace length = 0.8 cm; carapace width = 1 cm Description: thè body is subcircular in outline. The carapace has thè forni of a circular shield except for thè anterior frontal extension, covering part of thè head with antennules and antennae. The dorsal surface of carapace shows in thè centrai part a thin longitudinal ridge on its mediai! and posterior half, as well as a series of papillae located laterally and posteriorly. Even though thè large antennules are incomplete, they extend laterally from thè frontal exten¬ sion of thè head. The basai segment of thè peduncle is subquadrangular in out¬ line. The small antennae incomplete appear just dorsal and posterior to thè antennules. The maxillule and thè maxilla are not preserved, as well as thè tho- racopods. Discussion. The carapace outline allows to ascribe these specimens to thè order Cycloidea Glaessner, 1928 and thè morphological features are typical of thè family Cyclidae Packard, 1885, excluding their ascription to thè family Mesoprosopidae Glaessner, 1928 owing to thè pyriform carapace with postero- lateral spines, and to thè family Hemithrochiscidae Trauth, 1918 provided of carapace with large tubercles located along thè lateral margins, and rostral piate. Four genera belong to thè family Cyclidae Packard, 1885: Cyclus de Koninck, 1841, Halicyne von Meyer, 1844, Apionicon Schram, Vonk and Hof, 1977, and Carcinaspides Glaessner, 1969. The subcircular outline of thè cara¬ pace and thè lack of rostral piate exclude thè ascription of our specimens to Apionicon Schram, Vonk and Hof, 1977, thè unlobate margin exclude their ascription to Carcinaspides Glassner, 1969, and thè lack of underside of cara¬ pace with subparallel lamellae and thè dorsal surface of carapace slightly papil¬ lose exclude their ascription to Halicyne von Meyer, 1844. We ascribe tliem to Cyclus de Koninck, 1841 for thè subcircular outline of carapace, thè dorsal sur¬ face slightly papillose, and thè thin longitudinal ridge in mediali and posterior half of carapace. STUDIES ON PERMO-TRIAS OF MADAGASCAR Genus Halicyne von Meyer, 1844 Type species: Limulus agnotus von Meyer, 1838 Halicyne gondwanae n. sp. Figs. 3, 4 Diagnosis: carapace subcircular; dorsal surface of carapace strongly papillose and with a centrai triangolar papillose piate; underside of carapace in thè thoracic region marked by transverse lamellae. Etymology: thè trivial name refers to Gondwana, Continental mass to which Madagascar belongs. Holotype: MSNM il3280. Paratypes: MSNM Ì22868, Ì25461. Type locality. Mahatsara (Ifasy river); thè study specimens come from thè type locality studied by thè Department of thè Invertebrate Palaeontology of Museo di Storia Naturale di Milano during thè eighties of thè last century and collected directly in thè outcrop. Geological age: Olenekian (Lower Triassic). Occurrence and measurements: we ascribe to this species three specimens (MSNM il3280, Ì22868, Ì25461). MSNM il3280: carapace length = 1.5 cm; carapace width = 1.2 cm MSNM Ì22868: carapace length = 1 cm; carapace width = 1 cm MSNM Ì25461: carapace length = 1.5 cm; carapace width = 1 cm Fig. 3 - Distribution of thè nodules on thè ground in thè new erosion, located south of Mahatsara village. Fig. 3 - Distribuzione dei noduli sul terreno nella nuova erosione, localizzata a sud del villaggio di Mahatsara. 1 1 2 SILVIA BRAMBILLA, ALESSANDRO GARASSINO, GIOVANNI PASINI & GIORGIO TERUZZ1 db Fig. 4 - Cyclus madagascariensis n. sp., holotype, n. cat. MSNM Ì25462 (x7 ca.). Fig. 4 - Cyclus madagascariensis n. sp., olotipo, n. cat. MSNM Ì25462 (x7 ca.). Fig. 5 - Hcdicyne gondwanae n. sp.. holotype. n. cat. MSNM i 13280 (x4 ca.). Fig. 5 - Hcdicyne gondwanae n. sp., olotipo, n. cat. MSNM i 13280 (x4 ca.). STUDIES ON PERMO-TRIAS OF MADAGASCAR 113 Fig. 5 - Halicyne gondwanae n. sp., holotype, n. cat. MSNM i22868a (x4). Fig. 5 - Halicyne gondwanae n. sp., olotipo, n. cat. MSNM i22868a (x4). Description: thè body is subcircular in outline. The carapace has thè form of a subcircular shield as long as wide. The dorsal surface of carapace shows a strong papillose surface, as well as a centrai triangular papillose piate. The underside of thè carapace in thè region of thorax has a dense arrangement of sub- parallel lamellae. None of thè specimens preserve antennules and antennae, as well as maxillule and maxilla. The well-developed elongate five walking legs extend laterally from thè body. Furthemore, at least thè anterior-most of these have their distai extremities directed forward. Discussion. The morphological features observed in these specimens allow, like thè specimens ascribed to Cyclus de Koninck, 1841, to ascribe them to thè family Cycloidea Glaessner, 1928, excluding their attribution to thè other cycloid families. The subcircular outline of thè carapace and thè lack of rostral piate exclude their ascription to Apionicon Schram, Vonk and Hof, 1977, thè unlobate margin exclude their ascription to Carcinaspides Glassner, 1969, and thè lack of longitudinal ridge in median and posterior half of carapace, and thè dorsal surface of carapace strongly papillose exclude their ascription to Cyclus de Koninck, 1841. We ascribe them to Halicyne von Meyer, 1844 for thè subcir¬ cular outline of carapace, thè dorsal surface strongly papillose, thè underside of carapace with subparallel lamellae, and thè elongate walking legs. 1 14 SILVIA BRAMBILLA, ALESSANDRO GARASSINO, GIOVANNI PASINI & GIORGIO TERUZZI Acknowledgements We wish to thank R.M. Feldmann, Geology Department, Kent State University for thè useful advice in thè draft of manuscript, careful review and criticism ot manuscript. Photographic materials by L. Spezia and G. Pasini. References Bill P. 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