Brissid echinoid Eupatagus L. Agassiz, 1847 from The Khuiala Formation, Jaisalmer district, Rajasthan, India

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1 e-journal Earth ScienceIindia, Vol. I (II), 2008, pp Brissid echinoid Eupatagus L. Agassiz, 1847 from The Khuiala Formation, Jaisalmer district, Rajasthan, India D. K. Srivastava 1 and Hukam Singh 2 1 Centre of Advanced Study in Geology, University of Lucknow, Lucknow , India 2 Birbal Sahni Institute of Palaeobotany, Lucknow , India sirdkdr@gmail.com Abstract The spatangoid genus Eupatagus L. Agassiz, 1847 is recorded, for the first time, from the sediments of the Khuiala Formation (Early Eocene) exposed near Habur, Jaisalmer district, Rajasthan, India. The specimens are placed in a new species characterised by its large, oval test with mild frontal sinus; convex aboral surface; flat oral surface; anteriorly eccentric ethmolytic apical system; anteriorly eccentric kidney- shaped peristome; long, petaloid ambulacral petals; longitudinally oval periproct at the posterior truncation and imperforate, non crenulated tubercles. Introduction The paper records, for the first time, a brissid echinoid Eupatagus L. Agassiz, 1847 (Fischer,1966 and Smith, 2008) from the sediments of the Khuiala Formation (Early Eocene) exposed at about 625 m west of Habur, Jaisalmer district, Rajasthan, India (Fig.1) as Eupatagus rajasthanensis n. sp. The field work was carried out by the second author (HS) jointly with Dr. J. S. Guleria, Birbal Sahni Institute of Palaeobotany, Lucknow, while the palaeontological work has been carried out by the first author (DKS). Earlier, the three echinoid genera recorded from Rajasthan (Sahni, 1955; Sahni and Bhatnagar, 1958; Srivastava and Mathur, 1996 and Srivastava et al., 2008) are Recrosalenia (R. jaisalmerensis from the Jurassic sediments), Echinocyamus (E. jaisalmerensis from the Middle Eocene sediments) and Megapneustes (M. jaisalmerensis from the Early Eocene). However, the genus Eupatagus L. Agassiz, 1847 has so far been reported in India from the Tertiary rocks of Kachchh (Duncan and Sladen, 1883; Srivastava, 1981; Srivastava, 2004) and Assam (Spengler, 1923) only. Geology of the area The isolated outcrops of the fossiliferous Mesozoic and the Cenozoic formations in the Jaisalmer Basin are interspersed in the southeastern part of the basin within the desert sands (Singh, 2006). The Tertiary sequence in the Jaisalmer Basin (Das Gupta, 1974; Pareek, 1984; Singh, 1996; Singh, 2003; Sinha et al., 1998; Bhandari, 1999 and Singh, 2007) is represented by the Sanu, Khuiala, Bandha and Shumar formations in ascending order. The stratigraphic succession of the studied area is given in Table-1.

2 Brissid echinoid Eupatagus L. Agassiz, 1847 from the Khuiala Formation, Jaisalmer district, Rajasthan, India: D. K. Srivastava and Hukam Singh Fig.1: Geological map of the area showing the fossil locality (after Singh, 2007) Table- 1: Stratigraphic succession of the Palaeogene sediments in Jaisalmer area, Rajasthan, India Age Formation Member (Surface) Pleistocene to Shumar Sub-Recent Middle Eocene Bandah Bakhri Tibba Batrewala Limestone Early Eocene Khuiala Khinsar Palaeocene Cretaceous Sanu Abur/Pariwar Tetakkar Limestone Mohammaed Dhani Member (Subsurface) Bakhri Tibba Batrewala Limestone Upper Khinsar Sirhera Lower Khinsar Tetakkar Limestone Kharatar Mohammaed Dhani The age of echinoid-bearing horizon of the Khuiala Formation (calcareous sandy marl) is constrained by the presence of index larger foraminifer Assilina lacunata Cizancourt (Srivastava et al., 2008) which indicates an Early Eocene (Ypresian) age. The ostracode, bivalve and other biotic elements previously described from the Khuiala Formation (Khosla, 1972; Das Gupta, 1974; Pareek, 1984; Ghosh, 1987; Bhandari, 1995; Singh, 1996; Singh, 1997 and Singh, 2003) are also consistent with this age assignment.

3 e-journal Earth ScienceIindia, Vol. I (II), pp Systematic Palaeontology (Fischer, 1966) Order: Spatangoida Clauss, 1876 Family: Brissidae Gray, 1855 Genus: Eupatagus L. Agassiz, 1847 Subgenus: Eupatagus L. Agassiz, 1847 Eupatagus (Eupatagus) rajasthanensis sp. nov. (Figure 2. a-g) Material: 20 specimens, few broken and incomplete but preservation is fairly good; (Holotype: 7097/BSIP/39528; Paratypes: 7097/BSIP/39529 to 7097/BSIP/39547). Derivation of name: The species has been named after Rajasthan State (area of its occurrence), India. Diagnosis: The species is characterized by its large, oval test with mild frontal sinus; convex aboral surface; flat oral surface; anteriorly eccentric ethmolytic apical system; anteriorly eccentric kidney-shaped peristome; long, petaloid ambulacral petals; longitudinally oval periproct at the posterior truncation and imperforate, non crenulated tubercles. Description: The specimens are characterized by a large, oval test with mild frontal sinus, convex aboral surface, flat oral surface, highest point of the test at the centre of the test, margin tumid and well rounded. The test is longer than wide and wider than high, truncated towards posterior side and moderately keeled. Apical system anteriorly eccentric, ethmolytic with four small and circular genital pores, the two anterior genital pores are closer than the posterior ones. Paired ambulacra petaloid and flush with the test. Petal III indistinct, petals I & V longer than the petals II & IV. Poriferous zones slightly depressed and consists of inner circular and oval to slit like outer pores which are conjugated by a deep groove. Periproct longitudinally oval, lies on the vertical posterior truncation and not visible from the aboral side. Peristome on oral surface, anteriorly eccentric and kidneyshaped. The peripetalous fasciole passes around the petals and do not indent in the interambulacral areas. The subanal fasciole, however, is not visible. The test is ornamented with imperforate, non-crenulated tubercles which are sunken in small scrobicules. These are large, scarce and circumscribed by the peripetalous fasciole on the aboral side while orally these are dense and small. Dimensions (in mm): Specimen No. Length (L) Breadth (B) Height (H) Ratio between L, B & H 7097/BSIP (Holotype) /BSIP (Paratype)

4 Brissid echinoid Eupatagus L. Agassiz, 1847 from the Khuiala Formation, Jaisalmer district, Rajasthan, India: D. K. Srivastava and Hukam Singh Fig. 2: a-g Eupatagus (Eupatagus) rajasthanensis n. sp. (Scale bars = 5.0 mm otherwise as stated) a. Aboral view [7097/BSIP (Holotype)]; b. Apical disc (bar = 1.0 mm) [7097/BSIP (Paratype)]; c. Line drawing showing peripetalous fasciole; d. Aboral view showing ambulacral plates in petals IV & V [7097/BSIP (Paratype)]; e. Oral view showing plates around peristome [7097/BSIP 39531(Paratype)]; f. Posterior view showing periproct [7097/BSIP (Paratype)]; g. Lateral view [7097/BSIP (Holotype)]

5 e-journal Earth ScienceIindia, Vol. I (II), pp Remarks: The new species is close to E. alatus Arnold and Clark described from the Eocene sediments of Jamaica (Arnold and Clark, 1927) but it differs in having longer petals I & V, posteriorly protruded test and lesser number of tubercles. It also differs from Eupatagus cf. antillarum (Cotteau) reported from the mid-middle to low-late Eocene sediments of Clarimont Formation, White Limestone Group, Jamaica (Donovan and Rowe, 2000) in having less broad oval test which is broadest in the middle and more anteriorly eccentric apical system. Eupatagus (Eupatagus) rajasthanensis n. sp. differs from Eupatagus (Eupatagus) rostratus (d Archiac) reported from the Eocene and Oligocene (Srivastava, 2004) and Oligocene and Miocene rocks of Kachchh (Duncan & Sladen, 1883) in not having flexuous petals II & IV. It also differs from Eupatagus (Eupatagus) singhi Srivastava described from the Middle Oligocene sediments of Kachchh (Srivastava, 1981) in having moderate frontal sinus. Type locality: About 625 m west of Habur, Jaisalmer district, Rajasthan, India. Type horizon: Khuiala Formation (early Eocene). Repository All described, undescribed and photographed specimens of fossil echinoids (Holotype: 7097/BSIP/39528; Paratypes: 7097/BSIP/39529 to 7097/BSIP/39547) have been deposited in the Museum, Birbal Sahni Institute of Palaeobotany, Lucknow, India. Acknowledgements: The authors express a deep sense of gratitude to Prof. A. K. Jauhri, Head, Centre of Advanced Study in Geology, University of Lucknow, Lucknow and to Dr. N. C. Mehrotra, Director, Birbal Sahni Institute of Palaeobotany, Lucknow for providing facilities and encouragement. Dr. A. B. Smith (Natural History Museum, London) is thanked for critically reading through the original manuscript and offering helpful comments. They are obliged to Prof. Ashok Sahni, Panjab University, Chandigarh for suggestions. The financial assistance granted to the first author (DKS) by the Department of Science and Technology, New Delhi for the laboratory work is thankfully acknowledged. References Arnold, B. W. and Clark, H. L. (1927) Jamaican fossil echini, with descriptions of new species of Cainozoic echinoidea by H.L.Hawkins. Memoirs of the Museum of Comparative Zoology (Harvard), v. 50(1), pp. 63. Bhandari, A. (1995) Early Eocene ostracodes from the subsurface of Jaisalmer Basin, Rajasthan. Geosci. Jour., v. 15, pp Bhandari, A. (1999) Phanerozoic Stratigraphy of Western Rajasthan: A review. In: Kataria, P. (editor), Geology of Rajasthan-Status of Prespective, Proceedings of a Seminar (A.B. Roy Felicitation volume), pp Das Gupta, S. K. (1974) Stratigraphy of western Rajasthan Shelf. Proceedings IV th Colloquium Indian Micropaleontology and Stratigraphy, Dehradun, pp Donovan, S. K. and Rowe, C. D. (2000) Spatangoid echinoids from Eocene of Jamaica. J. Plaeont., v. 74(4), pp Duncan, P. M. and Sladen, W. P. (1883) The fossil Echinoidea of Kutch and Kattyawar. Palaeontologia Indica, v. 14, 104p, 13 pls. Fischer, A. G. (1966) Spatangoids. In: Moore, R. C. et al. (eds.), Treatise on Invertebrate Palaeontology, Part U(3), Echinodermata 3, Echinoidea, Geologial Society of America and University of Kansas Press, pp. U543 U628. Ghosh, C. C. (1987) Report of serpulid framestone from Khuiala Formation (lower Eocene) Jaisalmer Basin, Rajasthan. Curr. Sci., v. 56, pp Khosla, S. C. (1972) Ostracodes from the Eocene beds of Rajasthan. Microplaeontology, v. 18(4), pp

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