Palaeogeography, Palaeoclimatology, Palaeoecology 230 (2006) 243#250 www.elsevier.com/locate/palaeo Dinosaur sanctuary on the Chatham Islands, Southwest Pacific: First record of theropods from the K#T boundary Takatika Grit Jeffrey D. Stilwell a,b,*, Christopher P. Consoli a, Rupert Sutherland c, Steven Salisbury d, Thomas H. Rich e, Patricia A . Vickers-Rich a, Philip J. Currie f, Graeme J. Wilson c a School of Geosciences, M onash University, Clayton Victoria 3800 A ustralia b Centre for E volutionary R esearch, A ustralian Museum, 6 College St., Sydney N SWA ustralia c Institute of Geological and Nuclear Sciences, P . O. Box 30-368, L ower H utt, New Zealand d School of Life S ciences, The University of Queensland, Brisbane Qld 4072 A ustralia e Museum Victoria, P . O. Box 666E, M elbourne Victoria 3001 A ustralia f Royal Tyrrell M useum of Palaeontology, D rumheller, Alberta TOJ OYO Canada Received 3 March 2005; received in revised form 21 July 2005; accepted 27 July 2005 Abstract Cretaceous#Tertiary (K#T) boundary (ca. 65 Ma) sections on a Southwest Pacific island containing dinosaurs were unknown until March 2003 w hen theropod b ones w ere recovered from the Takatika Grit on the r emote Chatham Islands (latitude 448 S, longitude 1768 W), along the Chatham Rise. Tectonic and p alaeontologic evidence support the eastward extension of a ca. 900 km land b ridge that connected the islands to what is now New Zealand p rior to the K#T b oundary. The Chathams terrestrial fauna inhabited coastal, temperate environments along a low-lying, narrow, crustal extension ofthe New Zealand subcontinent, characterised by a tectonically dynamic, volcanic landscape w ith eroding hills (horsts) adjacent t o flood p lains and deltas, all sediments accumulating in grabens. This finger-like tract was b lanketed with a conifer and clubmoss (Lycopodiopsida) dominated forest. The Chatham Islands region would h ave, along with New Zealand, provided a dinosaur island sanctuary after separating from the Gondwana margin ca. 80 Ma. D 2005 Elsevier B.V. All r ights reserved. Keywords: Cretaceous#Tertiary b oundary; Dinosaur; Theropoda; Palaeobiogeography; Chatham Islands; New Zealand 1. Introduction Non-avian, terrestrial dinosaurs from the Mesozoic have not been p reviously reported from any oceanic islands in the Southwest Pacific, nor have any b irds. Terrestrial and marine deposits w ith latest Cretaceous * Corresponding author. Tel.: +61 3 9905 1642; fax: +61 3 9905 4903. E-mail address: [email protected] (J.D. Stilwell). 003 1-0182/$ - see front matter D 2005 Elsevier B.V. All r ights r eserved. doi: 10.1016/j.palaeo.2005.07.017 dinosaur remains are, in fact, rare in b oth hemispheres and are p articularly so in the south. Only a handful of localities are known to yield depauperate latest Creta- ceous faunas in presumed marine deposits from Haw- ke#s Bay in N orth Island, New Zealand (Molnar, 198 1; Scarlett and Molnar, 1984; Wiffen and Molnar, 1988; Molnar and Wiffen, 1994; Wiffen, 1996; Long, 1998); southern Patagonia (see Coria, 1999; Luna et al., 2003); and the James Ross Island group (Gasparini et al., 1987; Hooker et al., 1991; Case et al., 2000; Rich et al., 1999) (James, Seymour and Vega islands) along the tip of A ntarctic Peninsula. This report of latest Creta- 244 J.D. Stilwell et al. / Palaeogeography, P alaeoclimatology, P alaeoecology 230 (2006) 243$250 northwestern corner (see arrow). ceous dinosaurs in the Takatika Grit on the r emote Chatham Islands (Fig. 1) indicates t hat n on-avian ther- opods and other groups did exist on an island sanctuary for millions of y ears following the separation of New Zealand and the islands from the Gondwana margin. The Chatham Islands today are the eroded remnants of isolated oceanic isles that consist of a main island, Chatham (Rekohu in local Moriori language), and smal- ler island, Pitt (Rangiauria), located 22 km t o the southeast along with much smaller volcanic islets, reefs and rocks (Campbell et al., 1993). These islands are emergent, spectacular, low-lying, and steeply cliffed edifices at the eastern end of the Chatham Rise, a linear feature extending due east more than 1000 km from Canterbury Province of South Island, New Zealand. A major submarine extension of the New Zealand micro- continent, the Chatham Rise encompasses some 200,000 km (Wood and Herzer, 1993). Fortunately, the islands preserve an important Cretaceous to Recent record for this p art of the Pacific, w hich enables a detailed reconstruction of its geologic history over the last 100 Ma. The p refix for v ertebrate material GNS is an abbre- viation for the Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand. 2. Geology The geologic history of the Chatham Islands extends back into the late Paleozoic with exposed Torlesse ter- rane basement rocks equivalent to those on the New Zealand mainland (Hay et al., 1970; Campbell et al., 1993), consisting of greywacke, argillite and associated metamorphics, including the Chatham Schist. Resting unconformably on basement rocks is a thick sequence of Upper Cretaceous#Paleogene aged transgressive p ack- ets, derived from a p rincipal divergent tectonic p hase reflecting the final fragmentation of the Gondwana. This extensional regime resulted in substantial, east#west trending half-grabens and volcanism in the Bounty Trough#Chatham Rise region (Campbell et al., 1993). The Takatika Grit is a distinctive, thin, fossiliferous rock u nit (maximum thickness 10 m; Fig. 2.), a glau- conitic quartzofeldspathic grit made u p of sandstone and siltstones with a volcanogenic component, resting nonconformably on basement schist (Hay et al., 1970; Campbell et al., 1993). It hosts several b one horizons (Nodular Phosphorite-Bone Package (NPB)) spanning 2 km of wave-cut platform (between 43.7508S, 176.6678W and 43.7438S, 176.6838W) and p reserves skeletal elements, mainly of marine reptiles. Based on associated microfossil content, the unit is lower-Hau- with associated fossils (note: position of catalogued bones) and phosphorite nodules (see Legend). J.D. Stilwell et al. / Palaeogeography, P alaeoclimatology, P alaeoecology 230 (2006) 243#250 245 murian to mid-Teurian in age; the microfauna is dom- inated b y the Early Haumurian dinoflagellates, corre- lated to the Satyrodinium haumuriense Zone (Wilson, 1982; Wilson et al., 2005) (Haumurian#Teurian Stage, mid-Campanian to early Paleocene). The grit may rep- resent, in p art, an allochthonous accumulation of reworked u ppermost Cretaceous sediments and fossils that were deposited p ost K#T b oundary, in the Danian. However, the mixed latest Cretaceous#earliest Tertiary age of associated microfossils indicate that the K#T boundary may b e present b elow the exposed bone-rich beds. Vertebrate remains in the marine sediments include a theropod centrum (Fig. 3 A#B), the proximal p edal phalanx II-1 or III-1 ofa theropod (Fig. 3 F#G), as well as the probable theropod proximal head ofa tibia (Fig. 3 D# E) (all three elements from N PB). In slightly younger sediments, Greensand Package II, a theropod manual phalanx (Fig. 3 K#O) and manual ungual (Fig. 3 H#J) have b een recovered. These latter two b ones w ere col- lected stratigraphically above the major Cretaceous fau- nal assemblage in greensands together with rich dinoflagellate assemblages clearly of early-to mid-Teur- ian (Danian) age. Interestingly, these bones exhibit no signs of reworking. The latest Cretaceous theropod frag- ments were evidently transported into the shallow ma- rine environment from adjacent terrestrial habitats and display differential p reservation and wear. The b ones are associated with authigenic p hosphorite nodules of p eb- ble to boulder size and some of the nodules actually contain b one. 3. Dinosaurian elements GNS CD 578: a partial centrum, Theropoda; (Fig. 3 A#B). Measurements: Width (max)= 89.3 mm. Locality and horizon: N orthwest Chatham Island, New Zealand; Tioriori Group (Cretaceous#Tertiary); Taka- tika Grit (Lower Haumurian#Lower Danian); NPB in association with theropod dinosaur and marine reptile remains and p hosphorites nodules. Description: Theropod centrum with no trace of a neural arch or transverse p rocesses. Its p latycoelous articular surface could b e anterior or p osterior. The centrum is constricted at the anteroposterior midpoint as compared with its diameter at the articular end. There are no traces of a p neumatic fossa or p neumatic foram- ina p reserved on lateral side of the centrum. The cen- trum is hollow but no internal p artitions are p reserved, but given the state of preservation of this specimen, it is unlikely that such internal p artitions w ould have b een retained. Remarks: The centrum was from a medium-sized the- ropod about 4 m long and 3 m high, but its position along the vertebral column and orientation is difficult to determine due to its incomplete nature. The p latycoe- lous articular surface and constriction of the midpoint indicates that it is not an axial element of a marine reptile and the theropod caudal vertebra reported from Mangahouanga Stream, Hawke$s Bay, New Zealand bears no resemblance to the Chatham Island centrum (Molnar, 198 1). GNS CD 579: manual ungual, Theropoda; (Fig. 3 H#J). Measurements: Length= 15.25 mm, width=4.5 mm, height= 6.6 mm. Locality and horizon: N orthwest Chatham Island, New Zealand; Tioriori Group (Cretaceous#Tertiary); Taka- tika Grit (Lower Haumurian#Lower Danian); Green- sand Package II in association w ith fossil shark teeth and Danian microfossils. Description: A theropod m anual u ngual lacking the tip and distal-most portion of the dorsal surface; it is mediolaterally compressed, slightly asymmetric, and gently recurved.