The Mescal Cave Fauna (San Bernardino County, California) and testing assumptions of habitat fidelity in the Quaternary fossil record

2015 ◽  
Vol 83 (3) ◽  
pp. 582-587 ◽  
Author(s):  
Mary Allison Stegner
Keyword(s):  
Fossil Record ◽  
Mojave Desert ◽  
Time Averaging ◽  
San Bernardino County ◽  
Regional Patterns ◽  
Radiocarbon Dates ◽  
Neotoma Cinerea ◽  
Minimum Age ◽  
Habitat Fidelity ◽  
Faunal List

The late Pleistocene and Holocene vertebrate fossil record for the northern Mojave Desert (southwestern USA) is known primarily from five sites. Until now, only two of these have been radiometrically dated, and temporal placement of the others has been based on stratigraphic or biostratigraphic correlation, leading to circular interpretations of mammal extirpations in the Mojave. Here, I report a revised and complete faunal list for Mescal Cave, along with 22 AMS radiocarbon dates from 5 vertebrate taxa recovered from its deposits. The results reported here demonstrate time-averaging in Mescal Cave encompassing around ~ 34 ka, a maximum age 14 ka older and minimum age 10 ka younger than previously thought. Furthermore, radiocarbon analyses suggest local extirpation of Marmota flaviventris around 3.6 cal ka BP, considerably younger than expected based on regional patterns of warming and aridification in the Mojave. Conversely, radiocarbon dates from another presumably boreal species, Neotoma cinerea, are considerably older than expected, suggesting either that climate change at this site did not directly mirror regional patterns, that habitat requirements for these two species are not strictly boreal or cool/mesic as has often been assumed, or that local edaphic conditions and/or competitive interactions overrode the regional climatic controls on theses species' distribution.

Quantitative comparisons and models of time-averaging in bivalve and brachiopod shell accumulations

Paleobiology ◽  
2010 ◽  
Vol 36 (3) ◽  
pp. 428-452 ◽  
Author(s):  
Richard A. Krause ◽  
Susan L. Barbour ◽  
Michał Kowalewski ◽  
Darrell S. Kaufman ◽  
Christopher S. Romanek ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Time Averaging ◽  
Local Fauna ◽  
Stochastic Variation ◽  
Extrinsic Factors ◽  
Radiocarbon Dates ◽  
Frequency Distributions ◽  
Spatial And Temporal Scales ◽  
Deep Site ◽  
Age Frequency Distribution

The variation in time-averaging between different types of marine skeletal accumulations within a depositional system is not well understood. Here we provide quantitative data on the magnitude of time-averaging and the age structure of the sub-fossil record of two species with divergent physical and ecological characteristics, the brachiopodBouchardia roseaand the bivalveSemele casali.Material was collected from two sites on a mixed carbonate-siliciclastic shelf off the coast of Brazil where both species are dominant components of the local fauna.Individual shells (n= 178) were dated using amino acid racemization (aspartic acid) calibrated with 24 AMS radiocarbon dates. Shell ages range from modern to 8118 yearsb.p.for brachiopods, and modern to 4437 years for bivalves. Significant differences in the shape and central tendency of age-frequency distributions are apparent between each sample. Such differences in time-averaging magnitude confirm the assumption that taphonomic processes are subject to stochastic variation at all spatial and temporal scales. Despite these differences, each sample is temporally incomplete at centennial resolution and three of the four samples have similar right-skewed age-frequency distributions. Simulations of temporal completeness indicate that samples of both species from the shallow site are consistent with a more strongly right-skewed and less-complete age-frequency distribution than those from the deep site.We conclude that intrinsic characteristics of each species exert less control on the time-averaging signature of these samples than do extrinsic factors such as variation in rates of sedimentation and taphonomic destruction. This suggests that brachiopod-dominated and bivalve-dominated shell accumulations may be more similar in temporal resolution than previously thought, and that the temporal resolution of multi-taxic shell accumulations may depend more on site-to-site differences than on the intrinsic properties of the constituent organisms.

scholarly journals Unusual lizard fossil from the Miocene of Nebraska and a minimum age for cnemidophorine teiids

2020 ◽  
Vol 7 (8) ◽  
pp. 200317 ◽  
Author(s):  
Simon G. Scarpetta
Keyword(s):  
North America ◽  
Fossil Record ◽  
Fission Track ◽  
Divergence Time ◽  
Morphological Features ◽  
New Taxon ◽  
Fossil Material ◽  
Minimum Age ◽  
North And South America ◽  
North And South

Teiid lizards are well represented in the fossil record and are common components of modern ecosystems in North and South America. Many fossils were referred to the cnemidophorine teiid group (whiptails, racerunners and relatives), particularly from North America. However, systematic interpretations of morphological features in cnemidophorines were hampered by the historically problematic taxonomy of the clade, and the biogeography and chronology of cnemidophorine evolution in North America is poorly understood from the fossil record. Few fossil cnemidophorines were identified with an apomorphy-based diagnosis, and there are almost no fossil cnemidophorines that could be used to anchor node calibrations. Here, I describe a cnemidophorine from the Miocene Ogallala Group of Nebraska and diagnose the fossil using apomorphies. In that process, I clarify the systematic utility of several morphological features of cnemidophorine lizards. I refer the fossil to the least inclusive clade containing Aspidoscelis , Holcosus and Pholidoscelis . The most conservative minimum age of the locality of the fossil is a fission-track date of 6.3 Ma, but mammal biochronology provides a more refined age of 9.4 Ma, which can be used as a minimum age for the crown cnemidophorine clade in divergence time analyses. The fossil indicates that a cnemidophorine lineage that does not live in Nebraska today inhabited the area during the Miocene. I refrain from naming a new taxon pending discovery of additional fossil material of the lineage to which the fossil belonged.

Live, dead, and fossil mollusks in Florida freshwater springs and spring-fed rivers: Taphonomic pathways and the formation of multisourced, time-averaged death assemblages

Paleobiology ◽  
2020 ◽  
Vol 46 (3) ◽  
pp. 356-378
Author(s):  
Kristopher M. Kusnerik ◽  
Guy H. Means ◽  
Roger W. Portell ◽  
Mark Brenner ◽  
Quan Hua ◽  
...  
Keyword(s):  
Complex Mixture ◽  
Freshwater Ecosystems ◽  
Time Averaging ◽  
Multiple Sources ◽  
Near Surface ◽  
Radiocarbon Dates ◽  
Freshwater Gastropods ◽  
Melanoides Tuberculata ◽  
Death Assemblages

AbstractTaphonomic processes are informative about the magnitude and timing of paleoecological changes but remain poorly understood with respect to freshwater invertebrates in spring-fed rivers and streams. We compared taphonomic alteration among freshwater gastropods in live, dead (surficial shell accumulations), and fossil (late Pleistocene–early Holocene in situ sediments) assemblages from two Florida spring-fed systems, the Wakulla and Silver/Ocklawaha Rivers. We assessed taphonomy of two gastropod species: the native Elimia floridensis (n = 2504) and introduced Melanoides tuberculata (n = 168). We quantified seven taphonomic attributes (aperture condition, color, fragmentation, abrasion, juvenile spire condition, dissolution, and exterior luster) and combined those attributes into a total taphonomic score (TT). Fossil E. floridensis specimens exhibited the greatest degradation (highest TT scores), whereas live specimens of both species were least degraded. Specimens of E. floridensis from death assemblages were less altered than fossil specimens of the same species. Within death assemblages, specimens of M. tuberculata were significantly less altered than specimens of E. floridensis, but highly degraded specimens dominated in both species. Radiocarbon dates on fossils clustered between 9792 and 7087 cal BP, whereas death assemblage ages ranged from 10,692 to 1173 cal BP. Possible explanations for the observed taphonomic patterns include: (1) rapid taphonomic shell alteration, (2) prolonged near-surface exposure to moderate alteration rates, and/or (3) introduction of reworked fossil shells into surficial assemblages. Combined radiocarbon dates and taphonomic analyses suggest that all these processes may have played a role in death assemblage formation. In these fluvial settings, shell accumulations develop as a complex mixture of specimens derived from multiple sources and characterized by multimillennial time-averaging. These findings suggest that, when available, fossil assemblages may be more appropriate than death assemblages for assessing preindustrial faunal associations and recent anthropogenic changes in freshwater ecosystems.

Postglacial relative sea-level change, Port au Port area, west Newfoundland

1985 ◽  
Vol 22 (7) ◽  
pp. 1039-1047 ◽  
Author(s):  
I. A. Brookes ◽  
D. B. Scott ◽  
J. H. McAndrews
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
High Water ◽  
Relative Sea Level ◽  
Radiocarbon Dates ◽  
Ice Load ◽  
Bay Area ◽  
Port Area ◽  
Minimum Age ◽  
Late Wisconsinan

We first report pollen and foraminifera analyses and radiocarbon dates from two cores taken from salt-marsh deposits bordering Port au Port Bay, southwestern Newfoundland. Results show that relative sea level (RSL) stood at 2.8 m below present higher high-water level (HHWL) at 2770 ± 300 years BP and at −1.8 m at 2365 ± 175 years BP at the core sites. They permit calculation of a rate of late Holocene RSL change from western Newfoundland. We then report other available dates bearing on the earlier RSL record of this area.A date of 5800 ± 200 years BP fixes the age of minimum RSL in Port au Port Bay at 11–14 m below present. A date of 9350 ± 120 years BP from St. George's provides a minimum age for the passage of sea level below present there. A date of 12 600 ± 140 years BP from Stephenville fixes a sea level at 29 m above present, whereas one of 13 600 ± 110 years BP from Abrahams Cove dates the marine limit at 44 m. These geographically restricted data closely constrain a curve of postglacial RSL change in the Port au Port Bay – northern St. George's Bay area. The form of the curve supports a recent model predicting sea-level response to wastage of a limited late Wisconsinan ice load in the wider region.

Diversification of the greater hydrophilines clade of giant water scavenger beetles dated back to the Middle Eocene (Coleoptera:Hydrophilidae:Hydrophilina)

2010 ◽  
Vol 24 (1) ◽  
pp. 9 ◽  
Author(s):  
Martin Fikáček ◽  
Sonja Wedmann ◽  
Heiko Schmied
Keyword(s):  
Fossil Record ◽  
Middle Eocene ◽  
Sexually Dimorphic ◽  
Fossil Species ◽  
Minimum Age

Fossil representatives of the hydrophilid genera Hydrochara Berthold, 1827, Hydrobiomorpha Blackburn, 1888 and Hydrophilus Geoffroy, 1762 were recorded at the lower Middle Eocene locality Grube Messel in Germany. Four morphospecies were recognised, including Hydrobiomorpha eopalpalis, sp. nov. showing sexually dimorphic maxillary palpomere 2 unknown in any recent or fossil species of the genus. These fossils are the oldest known records of the mentioned genera and indicate a minimum age of 47 million years for the divergence of the Hydrobiomorpha and Hydrophilus clades. Based on these data, we assume that the diversification of the ‘greater hydrophilines’ clade predated the lower Middle Eocene. The fossil record of the subtribe Hydrophilina is briefly reviewed, the reasons of the scarcity or absence of some genera in the fossil record are discussed, and the paleoenviromental significance of the presented fossils is discussed.

The influence of lithification on Cenozoic marine biodiversity trends

Paleobiology ◽  
2009 ◽  
Vol 35 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Austin J. W. Hendy
Keyword(s):  
Fossil Record ◽  
Considerable Increase ◽  
Community Diversity ◽  
Marine Biodiversity ◽  
Time Averaging ◽  
Large Component ◽  
Late Mesozoic ◽  
Marine Communities ◽  
Fossil Material ◽  
The Difference

Recent research has corroborated the long-held view that the diversity of genera within benthic marine communities has increased from the Paleozoic to the Cenozoic as much as three- to fourfold, after mitigating for such biasing influences as secular variation in time-averaging and environmental coverage. However, these efforts have not accounted for the considerable increase in the availability of unlithified fossiliferous sediments in strata of late Mesozoic and Cenozoic age. Analyses presented here on the Cenozoic fossil record of New Zealand demonstrate that unlithified sediments not only increase the amount of fossil material and hence the observed diversity therein, but they also preserve a pool of taxa that is compositionally distinct from lithified sediments. The implication is that a large component of the difference in estimates of within-community diversity between Paleozoic and Cenozoic assemblages may relate to the increased availability of unlithified sediments in the Cenozoic.

The taphonomic clock in fish otoliths

Paleobiology ◽  
2021 ◽  
pp. 1-17
Author(s):  
Konstantina Agiadi ◽  
Michele Azzarone ◽  
Quan Hua ◽  
Darrell S. Kaufman ◽  
Danae Thivaiou ◽  
...  
Keyword(s):  
Fossil Record ◽  
Radiocarbon Dating ◽  
Pelagic Fish ◽  
Time Averaging ◽  
Target Species ◽  
Local Conditions ◽  
Preservation Potential ◽  
Species Population ◽  
Clock Hypothesis ◽  
Fish Otoliths

Abstract Paleobiological and paleoecological interpretations rely on constraining the temporal resolution of the fossil record. The taphonomic clock, that is, a correlation between the alteration of skeletal material and its age, is an approach for quantifying time-averaging scales. We test the taphonomic clock hypothesis for marine demersal and pelagic fish otoliths from a 10–40 m depth transect on the Mediterranean siliciclastic Israeli shelf by radiocarbon dating and taphonomic scoring. Otolith ages span the last ~8000 yr, with considerable variation in median and range along the transect. Severely altered otoliths, contrary to pristine otoliths, are likely to be older than 1000 yr. For pelagic fish otoliths, at 30 m depth, taphonomic degradation correlates positively with postmortem age. In contrast, no correlation occurs for demersal fishes at 10 and 30 m depth, mostly because of the paucity of very young pristine (<150 yr) otoliths, possibly due to a drop in production over the last few centuries. Contrary to molluscan and brachiopod shells, young otoliths at these depths are little affected and do not show a broad spectrum of taphonomic damage, because those that derive from predation are excreted in calcium- and phosphate-rich feces forming an insoluble crystallic matrix that increases their preservation potential. At 40 m depth, all dated otoliths are very young but rather damaged because of locally chemically aggressive sediments, thus showing no correlation between taphonomic grade and postmortem age. Our results show that local conditions and the target species population dynamics must be considered when testing the taphonomic clock hypothesis.

scholarly journals Corrigendum to “Radiocarbon dates of fossil record assigned to mylodontids (Xenarthra-Folivora) found in Cueva del Milodón, Chile” [Quat. Sci. Rev. 251 (2020) 106695]

2021 ◽  
Vol 258 ◽  
pp. 106886
Author(s):  
Leandro M. Pérez ◽  
Néstor Toledo ◽  
Florencia Mari ◽  
Ignacio Echeverría ◽  
Eduardo P. Tonni ◽  
...  
Keyword(s):  
Fossil Record ◽  
Radiocarbon Dates
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