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Haines E, Bailey E, Nelson J, Fenlon LR, Suárez R. Clade-specific forebrain cytoarchitectures of the extinct Tasmanian tiger. Proc Natl Acad Sci U S A 2023; 120:e2306516120. [PMID: 37523567 PMCID: PMC10410726 DOI: 10.1073/pnas.2306516120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 05/23/2023] [Indexed: 08/02/2023] Open
Abstract
The thylacine, or Tasmanian tiger, is the largest of modern-day carnivorous marsupials and was hunted to extinction by European settlers in Australia. Its physical resemblance to eutherian wolves is a striking example of evolutionary convergence to similar ecological niches. However, whether the neuroanatomical organization of the thylacine brain resembles that of canids and how it compares with other mammals remain unknown due to the scarcity of available samples. Here, we gained access to a century-old hematoxylin-stained histological series of a thylacine brain, digitalized it at high resolution, and compared its forebrain cellular architecture with 34 extant species of monotremes, marsupials, and eutherians. Phylogenetically informed comparisons of cortical folding, regional volumes, and cell sizes and densities across cortical areas and layers provide evidence against brain convergences with canids, instead demonstrating features typical of marsupials, and more specifically Dasyuridae, along with traits that scale similarly with brain size across mammals. Enlarged olfactory, limbic, and neocortical areas suggest a small-prey predator and/or scavenging lifestyle, similar to extant quolls and Tasmanian devils. These findings are consistent with a nonuniformity of trait convergences, with brain traits clustering more with phylogeny and head/body traits with lifestyle. By making this resource publicly available as rapid web-accessible, hierarchically organized, multiresolution images for perpetuity, we anticipate that additional comparative insights might arise from detailed studies of the thylacine brain and encourage researchers and curators to share, annotate, and preserve understudied material of outstanding biological relevance.
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Affiliation(s)
- Elizabeth Haines
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
| | - Evan Bailey
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
| | - John Nelson
- School of Biological Sciences, Monash University, Melbourne, Victoria, VIC3800, Australia
| | - Laura R. Fenlon
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
| | - Rodrigo Suárez
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, QLD4072, Australia
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Feigin C, Frankenberg S, Pask A. A Chromosome-Scale Hybrid Genome Assembly of the Extinct Tasmanian Tiger (Thylacinus cynocephalus). Genome Biol Evol 2022; 14:evac048. [PMID: 35349647 PMCID: PMC9007325 DOI: 10.1093/gbe/evac048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
The extinct Tasmanian tiger or thylacine (Thylacinus cynocephalus) was a large marsupial carnivore native to Australia. Once ranging across parts of the mainland, the species remained only on the island of Tasmania by the time of European colonization. It was driven to extinction in the early 20th century and is an emblem of native species loss in Australia. The thylacine was a striking example of convergent evolution with placental canids, with which it shared a similar skull morphology. Consequently, it has been the subject of extensive study. While the original thylacine assemblies published in 2018 enabled the first exploration of the species' genome biology, further progress is hindered by the lack of high-quality genomic resources. Here, we present a new chromosome-scale hybrid genome assembly for the thylacine, which compares favorably with many recent de novo marsupial genomes. In addition, we provide homology-based gene annotations, characterize the repeat content of the thylacine genome, and show that consistent with demographic decline, the species possessed a low rate of heterozygosity even compared to extant, threatened marsupials.
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Affiliation(s)
- Charles Feigin
- School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
- Department of Molecular Biology, Princeton University, New Jersey, USA
| | - Stephen Frankenberg
- School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Andrew Pask
- School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia
- Department of Sciences, Museums Victoria, Carlton, Victoria, Australia
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White LC, Saltré F, Bradshaw CJA, Austin JJ. High-quality fossil dates support a synchronous, Late Holocene extinction of devils and thylacines in mainland Australia. Biol Lett 2018; 14:rsbl.2017.0642. [PMID: 29343562 DOI: 10.1098/rsbl.2017.0642] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Accepted: 12/18/2017] [Indexed: 12/25/2022] Open
Abstract
The last large marsupial carnivores-the Tasmanian devil (Sarcophilis harrisii) and thylacine (Thylacinus cynocephalus)-went extinct on mainland Australia during the mid-Holocene. Based on the youngest fossil dates (approx. 3500 years before present, BP), these extinctions are often considered synchronous and driven by a common cause. However, many published devil dates have recently been rejected as unreliable, shifting the youngest mainland fossil age to 25 500 years BP and challenging the synchronous-extinction hypothesis. Here we provide 24 and 20 new ages for devils and thylacines, respectively, and collate existing, reliable radiocarbon dates by quality-filtering available records. We use this new dataset to estimate an extinction time for both species by applying the Gaussian-resampled, inverse-weighted McInerney (GRIWM) method. Our new data and analysis definitively support the synchronous-extinction hypothesis, estimating that the mainland devil and thylacine extinctions occurred between 3179 and 3227 years BP.
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Affiliation(s)
- Lauren C White
- Australian Centre for Ancient DNA, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia .,Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Saxony, Germany
| | - Frédérik Saltré
- Global Ecology, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
| | - Corey J A Bradshaw
- Global Ecology, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
| | - Jeremy J Austin
- Australian Centre for Ancient DNA, School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
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Newton AH, Spoutil F, Prochazka J, Black JR, Medlock K, Paddle RN, Knitlova M, Hipsley CA, Pask AJ. Letting the 'cat' out of the bag: pouch young development of the extinct Tasmanian tiger revealed by X-ray computed tomography. R Soc Open Sci 2018; 5:171914. [PMID: 29515893 PMCID: PMC5830782 DOI: 10.1098/rsos.171914] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 01/22/2018] [Indexed: 03/14/2024]
Abstract
The Tasmanian tiger or thylacine (Thylacinus cynocephalus) was an iconic Australian marsupial predator that was hunted to extinction in the early 1900s. Despite sharing striking similarities with canids, they failed to evolve many of the specialized anatomical features that characterize carnivorous placental mammals. These evolutionary limitations are thought to arise from functional constraints associated with the marsupial mode of reproduction, in which otherwise highly altricial young use their well-developed forelimbs to climb to the pouch and mouth to suckle. Here we present the first three-dimensional digital developmental series of the thylacine throughout its pouch life using X-ray computed tomography on all known ethanol-preserved specimens. Based on detailed skeletal measurements, we refine the species growth curve to improve age estimates for the individuals. Comparison of allometric growth trends in the appendicular skeleton (fore- and hindlimbs) with that of other placental and marsupial mammals revealed that despite their unique adult morphologies, thylacines retained a generalized early marsupial ontogeny. Our approach also revealed mislabelled specimens that possessed large epipubic bones (vestigial in thylacine) and differing vertebral numbers. All of our generated CT models are publicly available, preserving their developmental morphology and providing a novel digital resource for future studies of this unique marsupial.
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Affiliation(s)
- Axel H. Newton
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
- Melbourne Museum, Museums Victoria, Melbourne, Victoria, Australia
| | - Frantisek Spoutil
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague, Vestec, Czech Republic
| | - Jan Prochazka
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague, Vestec, Czech Republic
| | - Jay R. Black
- School of Earth Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | | | - Robert N. Paddle
- School of Psychology, Australian Catholic University, Melbourne, Victoria, Australia
| | | | - Christy A. Hipsley
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
- Melbourne Museum, Museums Victoria, Melbourne, Victoria, Australia
| | - Andrew J. Pask
- School of BioSciences, University of Melbourne, Melbourne, Victoria, Australia
- Melbourne Museum, Museums Victoria, Melbourne, Victoria, Australia
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