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- Kalthoff, Daniela, et al.
(författare)
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A new mammal from the Turonian–Campanian (Upper Cretaceous) Galula Formation, southwestern Tanzania
- 2019
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920. ; 64:1, s. 65-84
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Tidskriftsartikel (refereegranskat)abstract
- We here establish a newmammaliaform genus and species, Galulatheriumjenkinsi (Mammalia), from the UpperCretaceous Galula Formation in the Rukwa Rift Basin of southwestern Tanzania. Thisrepresents the first named taxon of a mammaliaform from the entire Late Cretaceous,an interval of 34 million years, of continental Afro-Africa. Preliminary studyof the holotype (a partial dentary) resulted in tentative assignation to the Gondwanatheria,a poorly known, enigmatic clade of Late Cretaceous–Paleogene Gondwanan mammals (Krauseet al. 2003). The application of advanced imaging (µCT) and visualizationtechniques permits a more detailed understanding of key anatomical features of thenew taxon. CT analysis reveals that the lower dentition consisted of a large,procumbent lower incisor and four cheek teeth, all which are ever growing(hypselodont). Importantly, all of the teeth appear to have been devoid ofenamel during life. Comparisons conducted with a range of Mesozoic and selectedCenozoic mammaliaform groups demonstrates that a number of features (e.g.,enamel-less and ever-growing teeth, columnar cheek teeth with relatively simpleocclusal morphology) expressed in Galulatheriumare reminiscent of disparate groups, making taxonomic assignment difficult. Hereinwe retain the provisional referral of Galulatherium(RRBP 02067) to Gondwanatheria; it is most similar to sudamericids such as Lavanify and Bharratherium from the Late Cretaceous of Madagascar and India,respectively, which exhibit relatively simple, high-crowned, columnar cheek teeth.Other features (e.g., enamel-less dentition) shared with disparate forms suchas the Late Jurassic Fruitafossor andvarious xenarthrans (e.g., sloths) are attributed to convergence. Detailed analysesof the depositional context for the type and only specimen place it as havinglived sometime between the late Turonian and latest Campanian (roughly 91–72million years ago). This enhanced geochronological context helps to refine thepalaeobiogeographical significance of Galulatheriumamong Cretaceous mammals in general and those of Gondwanan landmassesspecifically.
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- Kalthoff, Daniela, et al.
(författare)
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Complementary approaches to tooth wear analysisin Tritylodontidae (Synapsida, Mammaliamorpha)reveal a generalist diet.
- 2019
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Ingår i: PLOS ONE. - New York : Public Library of Science (PLoS). - 1932-6203. ; 14:7, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- Stereoscopic microwear and 3D surface texture analyses on the cheek teeth of ten Upper Triassic to Lower Cretaceous tritylodontid (Mammaliamorpha) taxa of small/medium to large body size suggest that all were generalist feeders and none was a dietary specialist adapted to herbivory. There was no correspondence between body size and food choice. Stereomicroscopic microwear analysis revealed predominantly fine wear features with numerous small pits and less abundant fine scratches as principal components. Almost all analyzed facets bear some coarser microwear features, such as coarse scratches, large pits, puncture pits and gouges pointing to episodic feeding on harder food items or exogenous effects (contamination of food with soil grit and/or dust), or both. 3D surface texture analysis indicates predominantly fine features with large void volume, low peak densities, and various stages of roundness of the peaks. We interpret these features to indicate consumption of food items with low to moderate intrinsic abrasiveness and can exclude regular rooting, digging or caching behavior. Possible food items include plant vegetative parts, plant reproductive structures (seeds and seed-bearing organs), and invertebrates (i.e., insects). Although the tritylodontid tooth morphology and auto-occlusion suggest plants as the primary food resource, our results imply a wider dietary range including animal matter.
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- Kalthoff, Daniela
(författare)
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Extinctions, genetic erosion and conservation options for the black rhinoceros (Diceros bicornis)
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322.
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Tidskriftsartikel (refereegranskat)abstract
- The black rhinoceros is again on the verge of extinction due to unsustainable poaching in its nativerange. Despite a wide historic distribution, the black rhinoceros was traditionally thought of asdepauperate in genetic variation, and with very little known about its evolutionary history. Thisknowledge gap has hampered conservation efforts because hunting has dramatically reduced thespecies' once continuous distribution, leaving five surviving gene pools of unknown genetic affinity.Here we examined the range-wide genetic structure of historic and modern populations using thelargest and most geographically representative sample of black rhinoceroses ever assembled. Usingboth mitochondrial and nuclear datasets, we described a staggering loss of 69% of the species'mitochondrial genetic variation, including the most ancestral lineages that are now absent frommodern populations. Genetically unique populations in countries such as Nigeria, Cameroon, Chad,Eritrea, Ethiopia, Somalia, Mozambique, Malawi and Angola no longer exist. We found that the historicrange of the West African subspecies (D. b. longipes), declared extinct in 2011, extends into southernKenya, where a handful of individuals survive in the Masai Mara. We also identify conservation unitsthat will help maintain evolutionary potential. Our results suggest a complete re-evaluation of currentconservation management paradigms for the black rhinoceros.
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- Kalthoff, Daniela
(författare)
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Feeding Ecology in Oligocene Mylodontoid Sloths (Mammalia,Xenarthra) as Revealed by Orthodentine Microwear Analysis
- 2018
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Ingår i: Journal of mammalian evolution. - : Springer Science and Business Media LLC. - 1064-7554 .- 1573-7055. ; 25:4, s. 551-564-
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Tidskriftsartikel (refereegranskat)abstract
- Recently, dental microwear analysis has been successfully employed to xenarthran teeth. Here, we present new data on use wear features on 16 molariforms of Orophodon hapaloides and Octodontotherium grande. These taxa count among the earliest sloths and are known from the Deseadan SALMA (late Oligocene). Modern phylogenetic analyses classify Octodontotherium and Orophodon within Mylodontoidea with whom they share lobate cheek teeth with an outer layer of cementum and a thick layer of orthodentine. Similar target areas of 100 μm2 were analyzed on the orthodentine surface of each tooth by stereomicroscopic microwear and by SEM microwear. Results were unlike those of extant sloths (stereomicroscopic microwear: Bradypus, Choloepus) and published data from fossil sloths (SEM microwear: Acratocnus, Megalonyx, Megatherium, Thinobadistes); thus, both approaches independently indicate a different feeding ecology for the Oligocene taxa. The unique microwear results suggest that both taxa fed on plant material with low to moderate intrinsic toughness (foliage, twigs) but also proposes intake of tougher food items (e.g., seeds). Frequent gouging of the tooth surfaces can be explained by exogenous influence on microwear, such as possible intake of abrasive grit. We suggest an unspecialized herbivorous diet for Octodontotherium and Orophodon utilizing diverse food resources of their habitat. These interpretations support the reconstruction of (1) Deseadan environments as open habitats with spreading savannas/grasslands and (2) both taxa as wide muzzled bulk feeders at ground level.
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- Kalthoff, Daniela
(författare)
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Modular Wear Facet Nomenclature for Mammalian post-canine dentitions
- 2017
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Ingår i: Historical Biology. - : Informa UK Limited. - 0891-2963 .- 1029-2381. ; 30:1-2, s. 30-41
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Tidskriftsartikel (refereegranskat)abstract
- Dental wear facets on the occlusal surface of premolars and molars are traces of their main function, themastication and therefore reflect masticatory movements and also paramasticatory (i.e. non-dietary useof teeth) behavior. Here we present the Modular Wear Facet Nomenclature applicable to most mammaliandentitions. Topographic positions of wear facets in relation to the major cusps and crests of the teeth areused to designate the areas of the occlusal surface the facets occupy (e.g. their mesial, distal, lingual, orbuccal position). Previous published systems for labeling wear facets have been inconsistent with eachother. Therefore, we provide a synoptic review of the most widely-used terminologies, and introducethe alternative Modular Wear Facet Nomenclature. This nomenclature aims to overcome the difficultiescaused by the existing inconsistent wear facet terminologies. Our new approach is applicable to dentitionswhere the occlusal morphology does not change significantly for most of the lifetime of the animal. Inthose dentitions, the primary occlusal surfaces are not significantly modified as wear facets become moreextensive with wearing. This appears to be a common pattern in pre-tribosphenic, tribosphenic molars,and the teeth derived from tribosphenic precursors (e.g. bunodont molar morphologies). In teeth wherethe secondary occlusal surface is functionally intensely modified (i.e. high-crowned and evergrowingteeth with large areas of dentine exposed) any facet labeling system appears to be challenging, since theidentification of individual facets is blurred and their spatial position may be indeterminable.
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| 11. |
- Mörs, Thomas, 1962-, et al.
(författare)
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A new large beaver (Mammalia, Castoridae) from the Early Miocene of Japan
- 2016
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Ingår i: Journal of Vertebrate Paleontology. - : Society of Vertebrate Paleontology. - 0272-4634 .- 1937-2809.
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Tidskriftsartikel (refereegranskat)abstract
- A new early Miocene large castorid, Minocastor godai gen. et sp. nov., from the Dota locality, Gifu Prefecture in central Japan, is described on the basis of dentaries and teeth. The material comes from the Kani basin, where limnofluviatile clay and sandstones of the Nakamura Formation (Mizunami Group) are exposed on the southern (left) bank of the Kiso River. It represents the richest sample of a Miocene small mammal in the Japanese fossil record thus far known. Based on jaw and tooth morphology, this new castorid most likely represents a primitive anchitheriomyine. However, it lacks the marked striations on the incisors that are characteristic of the advanced large, middle Miocene anchitheriomyines like Anchitheriomys and Amblycastor. The new castorid shares this dental feature with other primitive anchitheriomyines from Asia and North America, like Propalaeocastor, Oligotheriomys, and Miotheriomys. For these genera, a new tribe, Minocastorini, is proposed as sister group to the Anchitheriomyini. The incisor enamel microstructure of the new castorid largely exhibits plesiomorphic characters but also apomorphic features such as pseudo-pauciserial Hunter-Schreger bands. Additionally, the outer portion of the enamel band is rather thick in comparison to that of other beavers. Based on the rodent taxa associated with Minocastor godai gen. et sp. nov., Dota can be correlated with European Neogene mammal units MN 3/4. Magnetostratigraphic studies and radiometric dates obtained from the Mizunami Group indicate that Dota is more likely correlated with MN 3, with an absolute age of around 18.5 Ma.
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| 12. |
- Palkopoulou, Eleftheria, et al.
(författare)
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Synchronous genetic turnovers across Western Eurasia in Late Pleistocene collared lemmings
- 2016
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 22:5, s. 1710-1721
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Tidskriftsartikel (refereegranskat)abstract
- Recent palaeogenetic studies indicate a highly dynamic history in collared lemmings (Dicrostonyx spp.), with several demographical changes linked to climatic fluctuations that took place during the last glaciation. At the western range margin of D.torquatus, these changes were characterized by a series of local extinctions and recolonizations. However, it is unclear whether this pattern represents a local phenomenon, possibly driven by ecological edge effects, or a global phenomenon that took place across large geographical scales. To address this, we explored the palaeogenetic history of the collared lemming using a next-generation sequencing approach for pooled mitochondrial DNA amplicons. Sequences were obtained from over 300 fossil remains sampled across Eurasia and two sites in North America. We identified five mitochondrial lineages of D.torquatus that succeeded each other through time across Europe and western Russia, indicating a history of repeated population extinctions and recolonizations, most likely from eastern Russia, during the last 50000years. The observation of repeated extinctions across such a vast geographical range indicates large-scale changes in the steppe-tundra environment in western Eurasia during the last glaciation. AllHolocene samples, from across the species' entire range, belonged to only one of the five mitochondrial lineages. Thus, extant D.torquatus populations only harbour a small fraction of the total genetic diversity that existed across different stages of the Late Pleistocene. In North American samples, haplotypes belonging to both D.groenlandicus and D.richardsoni were recovered from a Late Pleistocene site in south-western Canada. This suggests that D.groenlandicus had a more southern and D.richardsoni a more northern glacial distribution than previously thought. This study provides significant insights into the population dynamics of a small mammal at a large geographical scale and reveals a rather complex demographical history, which could have had bottom-up effects in the Late Pleistocene steppe-tundra ecosystem.
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- van der Valk, Tom, et al.
(författare)
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Significant loss of mitochondrial diversity within the last century due to extinction of peripheral populations in eastern gorillas
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Species and populations are disappearing at an alarming rate as a direct result of human activities. Loss of genetic diversity associated with population decline directly impacts species’ long-term survival. Therefore, preserving genetic diversity is of considerable conservation importance. However, to assist in conservation efforts, it is important to understand how genetic diversity is spatially distributed and how it changes due to anthropogenic pressures. In this study, we use historical museum and modern faecal samples of two critically endangered eastern gorilla taxa, Grauer’s (Gorilla beringei graueri) and mountain gorillas (Gorilla beringei beringei), to directly infer temporal changes in genetic diversity within the last century. Using over 100 complete mitochondrial genomes, we observe a significant decline in haplotype and nucleotide diversity in Grauer’s gorillas. By including historical samples from now extinct populations we show that this decline can be attributed to the loss of peripheral populations rather than a decrease in genetic diversity within the core range of the species. By directly quantifying genetic changes in the recent past, our study shows that human activities have severely impacted eastern gorilla genetic diversity within only four to five generations. This rapid loss calls for dedicated conservation actions, which should include preservation of the remaining peripheral populations.
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