Rapid growth in Late Cretaceous sea turtles reveals life history strategies similar to extant leatherbacks (original) (raw)
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PROCEEDINGS OF THE NINETEENTH ANNUAL SYMPOSIUM ON SEA TURTLE CONSERVATION AND BIOLOGY
TM 443:101-103, 1999
NOAA NMFS - 443 PP. 101-103 "The first described fossilized sea turtle nests occur as sedimentary structures preserved in the Fox Hills Sandstone, Elbert County, Colorado. They are Cretaceous analogs to Recent loggerhead sea turtle nests studied on St. Catherines Island, GA (Marsh and Bishop, 1993). Although sea turtles have an extensive geological record extending at least into the Jurassic and Early Cretaceous (Nicholls, 1997; Hirayama, 1997), traces of their terrestrial nesting activities (Caldwell, Carr, and Ogren, 1959; Witherington [and Witherington, 2016]; Hailman and Elowson, 1992) have not been well documented in the literature and fossil traces have only recently been described (Bishop et al., 1997, [ 2011])." N.B. Abstract slightly modified to new literature.
The shell bone histology of fossil and extant marine turtles revisited
Biological Journal of The Linnean Society, 2014
Modern turtles exhibit a broad scope of ecological adaptations, including coastal marine and pelagic habitats, and, during their evolutionary history, turtles repeatedly exploited the aquatic environment as well. Although some pleurodiran clades also ventured into the marine realm, it is the cryptodires that did so most extensively. Among those, three major radiation phases are distinguished, with the first phase consisting of basal eucryptodiran taxa inhabiting littoral or near costal environments (Late Jurassic, Europe); the second phase including more open marine chelonioids (starting in the late Early Cretaceous, mainly North America and Eurasia); and the third phase (starting in the Palaeocene/Eocene, global distribution) including the highly-nested chelonioids, such as the modern cheloniid and dermochelyid turtles and closest relatives. A review of previously published as well as unpublished data of shell microstructures of these groups and those of some of the earliest aquatic turtles from the Middle Jurassic, Heckerochelys romani and Eileanchelys waldmani, show that bones are strongly influenced functionally as a result of life spent in an aquatic medium, whereas there are little to no characters of systematic value in the bones. We confirm the general tetrapod pattern that pelagic forms tend to show osteoporotic-like shell structures and neritic forms tend to have more bone ballast, especially by retaining a thickened external compacta.
Three Ways to Tackle the Turtle: Integrating Fossils, Comparative Embryology, and Microanatomy
Vertebrate Paleobiology and Paleoanthropology, 2012
Herein we review a series of case studies covering the evolution and phylogenesis of turtles, and the ontogenetic development of one of the most peculiar body plans within the Craniota. Comparative analyses of skeletal development, ontogenetic timing, and bone microstructure in both extant and extinct taxa are used to document patterns and make inferences about the origin of turtles, turtle ingroup relationships, and the evolution of turtle ontogenetic development. The need for a balanced sampling of both cryptodiran and pleurodiran turtle species for future comparative studies is highlighted.
THE ORIGIN AND EARLY EVOLUTION OF TURTLES
Annual Review of Ecology and Systematics, 1999
A critical reexamination of turtle relationships continues to support a sister-group relationship of turtles with a clade of marine reptiles, Sauropterygia, within crown-group Diapsida (Sauria). The high Homoplasy Index raises concerns about the phylogenetic information content of various morphological characters in broadscale phylogenetic analyses. Such analyses may also suffer from inadequate statements of primary homology. Several such statements that have played an important role in the analysis of turtle relationships (dermal armor, acromion, astragalo-calcaneal complex, hooked fifth metatarsal) are reviewed in detail. An evolutionary scenario for the origin of the turtle bauplan suggests an aquatic origin of turtles, which is supported not only by their sauropterygian relationships, but also by paleobiogeographic and stratigraphic considerations. However, turtle relationships remain labile, and further investigations of their relationships are required, involving molecular and physiological data.
2018 Frazier et al (Remains of Leatherback turtles, Dermochelys coriacea__RH-6 and HD-6).pdf
PeerJ, 2018
Small, irregular isolated bones identified as remains of leatherback turtles (Dermochelys coriacea) were recovered from Mid to Late Holocene sites at Ra’s al-Hamra and Ra’s al-Hadd, coastal Oman. These provide the third instance of this animal being documented from any prehistoric site anywhere, and the records provide one of the oldest, if not the oldest, dates for this distinctive chelonian—even though they do not refer to fossils. Decades of research in this region has yielded vast amounts of archaeological information, including abundant evidence of intense exploitation and utilization of marine turtles from about 6,500 to 4,000 BP. During part of this period, turtle remains in human burials have been extraordinary; the turtle involved, Chelonia mydas, has been abundant in the region during modern times. Yet despite intense and varied forms of prehistoric marine resource exploitation, and major, long-term archaeological work, no other turtle species has been previously authenticated from these, or other coastal sites. The documentation of remains of the largest and most distinctive of living marine turtles, D. coriacea, at Ra’s al-Hamra and Ra’s al-Hadd, presented herein, provide detailed information that serves as the basis for future interpretations and discussions regarding incomplete, disarticulated remains from the Mid to Late Holocene, particularly in reference to taphonomic questions and diverse environmental conditions.
Time in tortoiseshell: a bomb radiocarbon-validated chronology in sea turtle scutes
Proceedings of the Royal Society B, 2016
Some of the most basic questions of sea turtle life history are also the most elusive. Many uncertainties surround lifespan, growth rates, maturity and spatial structure, yet these are critical factors in assessing population status. Here we examine the keratinized hard tissues of the hawksbill (Eretmochelys imbricata) car-apace and use bomb radiocarbon dating to estimate growth and maturity. Scutes have an established dietary record, yet the large keratin deposits of hawksbills evoke a reliable chronology. We sectioned, polished and imaged posterior marginal scutes from 36 individual hawksbills representing all life stages, several Pacific populations and spanning eight decades. We counted the apparent growth lines, microsampled along growth contours and calibrated D 14 C values to reference coral series. We fit von Bertalanffy growth function (VBGF) models to the results, producing a range of age estimates for each turtle. We find Hawaii hawksbills deposit eight growth lines annually (range 5–14), with model ensembles producing a somatic growth parameter (k) of 0.13 (range 0.1–0.2) and first breeding at 29 years (range 23–36). Recent bomb radio-carbon values also suggest declining trophic status. Together, our results may reflect long-term changes in the benthic community structure of Hawaii reefs, and possibly shed light on the critical population status for Hawaii hawksbills.
Stage durations are integral to wildlife population models that can inform management, as they influence age at maturation and stage-specific survival rates. To refine oceanic stage duration estimates for western North Atlantic loggerhead sea turtles Caretta caretta, skeletochronological analysis was conducted on humeri collected in the Azores islands and along the US Atlantic coast. Complementary skeletal growth increment-specific stable isotope analysis was also performed for a sub-set of the humeri, to identify the skeletal growth mark associated with the shift from oceanic to neritic habitat through stable nitrogen isotope (δ 15 N) values and the presence of turtles in inshore waters. Although the transitional growth mark in this sub-sample corresponded to a range of sizes similar to those described in previous studies, mean size at recruitment (55.3 cm straightline carapace length [SCL]) for these turtles was larger than previously estimated. Similarly, while the range of ages at recruitment -corresponding both with the transitional growth mark and those yielded by fitting smoothing splines to SCL-at-age data -overlapped almost fully with earlier estimates, the mean age estimate (12.4 yr) differed from previous studies. Validated back-calculation of somatic growth rates from skeletal growth marks yielded means and ranges that encompassed those of previous loggerhead growth studies in this geographic area. Generalized additive models and generalized additive mixed models used to assess the potential influence of discrete and continuous covariates on back-calculated growth rates spanning 1984 to 2009 indicated significant effects of age, SCL, calendar year, and δ 15 N, but none for sex or location.