Diagenesis has been recognized for decades to significantly alter the trace elements biogenic signatures in fossil tooth enamel and bone that are routinely used for paleobiological and paleoenvironmental reconstructions. This signature is modified during diagenesis according to a complex continuum between two main processes, addition and substitution. For an additive-like, or early diagenesis, the trace elements biogenic profiles can be restored by leaching secondary minerals, but this technique is inefficient for a substitutive-like, or extensive diagenesis for which secondary trace elements are incorporated into the biogenic mineral. This scheme is however unclear for Ca, the major cation in tooth enamel and bone hydroxylapatite, whose stable isotope composition (δ44/42Ca) also conveys biological and environmental information. We present a suite of leaching experiments for monitoring δ44/42Ca values in artificial and natural fossil enamel and bone from different settings. The results show that enamel δ44/42Ca values are insensitive to an additive-like diagenesis that involves the formation of secondary Ca- carbonate mineral phases, while bone shows a consistent offset toward 44Ca-enriched values, that can be restored to the biogenic baseline by a leaching procedure. In the context of a substitutive-like diagenesis, bone exhibits constant δ44/42Ca values, insensitive to leaching, and shows a REE pattern symptomatic of extensive diagenesis. Such a REE pattern can be observed in fossil enamel for which δ44/42Ca values are still fluctuating and follow a trophic pattern. We conclude that Ca isotopes in fossil enamel are probably not prone to extensive diagenesis and argue that this immunity is due to the very low porosity of enamel that cannot accommodate enough secondary minerals to significantly modify the isotopic composition of the enamel Ca pool.
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RBINS Staff Publications 2023
We describe Gekko dam sp. nov. based on type specimens from a limestone hill in Palian District, Trang Province, southern peninsular Thailand. The new species is also found in Satun Province, southern peninsular Thailand, and in Perlis State, northwestern Peninsular Malaysia. A member of the subgenus Gekko, it differs from all currently recognized Gekko species by the following combination of morphological characters and pattern: maximal known snout-vent length of 149.1 mm, lack of contact between nostrils and rostral, 21–24 interorbital scales between supraciliaries, 72–83 scale rows around midbody, 12–14 dorsal tubercle rows at midbody, 26–28 ventral scale rows at midbody, 22 precloacal pores in males, two postcloacal tubercles on each side of the base of the tail, 14–17 subdigital lamellae on 1st toe and 19–21 on 4th toe, a Y-shaped mark on head, white spots on head, dark grey to black dorsal background with four regular bands of contrasting white spots on dorsum between limb insertions, throat and venter white with orange patches, and a copper iris.
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RBINS Staff Publications 2026
