Short-tailed whipscorpions are a small arachnid order with 379 described species from (sub)tropical regions of the world. The order has a fragmentary fossil record but has left a rich, albeit hitherto undocumented, fossil legacy in mid-Cretaceous amber from Myanmar, also called Burmese amber or Burmite. Here, we review a large series of schizomids from this type of amber and propose four new genera for seven new species. In addition, we include a short revision of all schizomid genera based on 14 morphological characters. Although none of the fossils can be assigned to Recent genera, they resemble the modern fauna in general morphology and highlight relative morphological stasis in this arachnid order. The fossils show a general trend towards eye reduction, but some of the specimens retain corneate eyes. Comparative data suggest affinities of the fossils with the Recent Old World fauna rather than American relatives. Furthermore, the fossils provide evidence for a Gondwanan origin of the Burma Terrane. Overall, the data suggest a high diversity at both species and genus levels for Burmese amber schizomids. We discuss potential reasons for this richness that will probably necessitate the description of additional genera and species in future studies.
Loose limestone blocks of a newly recognized hydrocarbon-seep deposit from the lower Oligocene Jansen Creek Member of the Makah Formation were collected on a beach terrace close to the mouth of Bullman Creek in Washington State, USA. The limestone consists largely of authigenic carbonate phases, including 13C-depleted fibrous cement forming banded and botryoidal crystal aggregates with δ13C values as low as –23.5 ‰. Lipids extracted from the limestone yielded molecular fossils of anaerobic methanotrophic archaea (ANME), dominated by compounds of an ANME-2/DSS consortium with δ13C values as low as −106 ‰, indicating formation at an ancient methane seep. The fossil inventory of the seep deposit is remarkable, consisting almost solely of echinoid remains, whereas typical seep biota are absent. Varying preservation of the echinoid fossils indicates parautochthonous deposition, corroborated by evidence for high fluid flow at the ancient seep, possibly responsible for displacement of echinoids after death. Although a full taxonomic description of the echinoids cannot be given, almost all fossils were assigned to one taxon of irregular spatangoids, except for a single regular echinoid. Abundance and lifestyle of the irregular spatangoids in the Bullman Creek echinoid seep deposit resemble those of the fossil Tithonia oxfordiana from an upper Jurassic seep deposit in France and extant Sarsiaster griegii from modern seeps in the Gulf of Mexico. The Bullman Creek echinoid deposit probably represents a fossil analogue of the Gulf of Mexico Sarsiaster mass occurrence, indicating that the adaptation of spatangoid echinoids to chemosynthesis-based ecosystems ranges back at least to the earliest Oligocene.
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