Surculichnus bifurcauda n. igen., n. isp., a trace fossil from Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, USA, attributed to notostracan crustaceans based on neoichnological experimentation Richard J. Knecht a , Jacob S. Benner a, ⁎, D. Christopher Rogers b , John C. Ridge a a Department of Geology, Tufts University, Lane Hall, Medford, MA 02155, United States b EcoAnalysts, Inc., 1307 “L” St., Davis, CA 95616, United States abstract article info Article history: Received 2 February 2008 Received in revised form 22 July 2008 Accepted 24 October 2008 Keywords: Trace fossils New England Pleistocene Glacial lake Varves Neoichnology Notostraca Surculichnus bifurcauda New trace fossils found in the Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, Vermont, USA represent the first known notostracan presence in glacial Lake Hitchcock. These unique trace fossils warrant a new ichnogenus and ichnospecies Surculichnus bifurcauda. The New England Varve Chronology (NEVC) constrains the initial presence of S. bifurcauda at ∼ 13.3–13.2 kyr. The morphology of S. bifurcauda correlates well with notostracan characteristics and behavior. Sieving of bedding planes that contained S. bifurcauda produced one chitinous fossil that is suggestive of a notostracan telson. Neoichnological experimentation was conducted with the species Triops longicaudatus. During the subadult stage, T. longicaudatus produced traces representative of locomotion and feeding behaviors, and at the adult stage reproduced S. bifurcauda, as well as Rusophycus. Possible explanations for the productions of these traces are egg laying or predation behaviors that are both related to maturity. Further research in the paleo- and modern ecology of glacial and nearctic lakes may shed more light on the maker of S. bifurcauda. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Paleontological studies of varved sediments provide paleobiogeo- graphical and paleoenvironmental data with high temporal resolu- tion. Trace fossils, which are readily preserved in varved glaciolacustrine sediment, can provide proxy faunal data in the absence of a complete body fossil record. Recent studies of trace fossils from the varves of glacial Lake Hitchcock, New England, USA, have provided much new information on the benthos of this late Pleistocene lake, particularly with respect to its piscine inhabitants (Benner and Ridge, 2004; Benner et al., 2006, 2008, this issue). New trace fossils discovered in the Connecticut River Valley (CRV) varves now add to the developing picture of this late Pleistocene ecosystem. The purpose of this paper is to introduce a new ichnogenus and ichnospecies, and to describe its mode of occurrence and probable tracemaker: a notostracan crustacean. A number of trace fossils attrib- uted to notostracans are compared to the Pleistocene specimens and reconciled with neoichnological experimentation and with potential body fossils recovered from the varves. 2. Geological setting The trace fossils of interest come from varves deposited in glacial Lake Hitchcock, a Late Pleistocene glacial lake that occupied portions of the CRV of Connecticut, Massachusetts, New Hampshire and Ver- mont, USA (Ashley, 1975; Ridge and Larsen, 1990; Stone and Ashley, 1992; Stone et al.,1998; Ridge et al., 1999; Ridge, 2003, 2004). Varves deposited in the CRV and associated tributaries are numbered using a floating time scale (Antevs, 1922, 1928) called the New England (NE) Varve Chronology (NEVC). Varve years are preceded by NE, indicating years in the New England Varve Chronology, which is numbered from oldest to youngest as NE2701–7750. The NEVC is calibrated based on radiocarbon ages (Ridge and Larsen, 1990; Ridge and Toll, 1999; Ridge et al., 1999, 2001; Ridge, 2003, 2004) for which calendar years have been estimated using the CALIB 5.01 program (Stuiver and Reimer, 1993; Stuiver et al., 1998; Reimer et al., 2004). Unless otherwise specified, all numerical ages given in this paper are in estimated calendar years given as kyr before present (kyr). Water depth estimates given were calculated by subtracting elevations of varves from lake surface elevation as indicated by deltaic topset–foreset contacts. Two sites in Vermont yielded specimens for this study (Fig. 1). Site WR-1 is a sand and gravel pit located in the Wells River Valley, a tributary of the Connecticut River, 2.6 km west of the town of Wells River, Vermont (44.1539°N, 72.0737°W). The WR-1 locality preserves Palaeogeography, Palaeoclimatology, Palaeoecology 272 (2009) 232–239 ⁎ Corresponding author. E-mail address: jacob.benner@tufts.edu (J.S. Benner). 0031-0182/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2008.10.013 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo