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Chuong CM, Wu P, Yu Z, Liang YC, Widelitz RB. Organizational principles of integumentary organs: Maximizing variations for effective adaptation. Dev Biol 2025; 522:171-195. [PMID: 40113027 DOI: 10.1016/j.ydbio.2025.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2024] [Revised: 03/16/2025] [Accepted: 03/17/2025] [Indexed: 03/22/2025]
Abstract
The integument serves as the interface between an organism and its environment. It primarily comprises ectoderm-derived epithelium and mesenchyme derived from various embryonic sources. These integumentary organs serve as a barrier defining the physiological boundary between the internal and exterior environments and fulfill diverse functions. How does the integument generate such a large diversity? Here, we attempt to decipher the organizational principles. We focus on amniotes and use appendage follicles as the primary examples. The integument begins as a simple planar sheet of coupled epithelial and mesenchymal cells, then becomes more complex through the following patterning processes. 1) De novo Turing periodic patterning process: This process converts the integument into multiple skin appendage units. 2) Adaptive patterning process: Dermal muscle, blood vessels, adipose tissue, and other components are assembled and organized around appendage follicles when present. 3) Cyclic renewal: Skin appendage follicles contain stem cells and their niches, enabling physiological molting and regeneration in the adult animal. 4) Spatial variations: Multiple appendage units allow modulation of shape, size, keratin types, and color patterns of feathers and hairs across the animal's surface. 5) Temporal phenotypic plasticity: Cyclic renewal permits temporal transition of appendage phenotypes, i.e. regulatory patterning or integumentary metamorphosis, throughout an animal's lifetime. The diversities in (4) and (5) can be generated epigenetically within the same animal. Over the evolutionary timescale, different species can modulate the number, size, and distributions of existing ectodermal organs in the context of micro-evolution, allowing effective adaptation to new climates as seen in the variation of hair length among mammals. Novel ectodermal organs can also emerge in the context of macro-evolution, enabling animals to explore new ecological niches, as seen in the emergence of feathers on dinosaurs. These principles demonstrate how multi-scale organ adaption in the amniotes can maximize diverse and flexible integumentary organ phenotypes, producing a vast repertoire for natural selection and thereby providing effective adaptation and evolutionary advantages.
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Affiliation(s)
- Cheng Ming Chuong
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA.
| | - Ping Wu
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Zhou Yu
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Ya-Chen Liang
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Randall B Widelitz
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
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Marchetti L, Logghe A, Buchwitz M, Fröbisch J. Early Permian synapsid impressions illuminate the origin of epidermal scales and aggregation behavior. Curr Biol 2025:S0960-9822(25)00574-3. [PMID: 40412378 DOI: 10.1016/j.cub.2025.04.077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2025] [Revised: 03/24/2025] [Accepted: 04/30/2025] [Indexed: 05/27/2025]
Abstract
Fossil evidence of skin structure1,2 and group behavior3,4 in the stem group of mammals, the early synapsids, is sparse and restricted to a few occurrences. We describe here exceptional resting trace fossils, Bromackerichnus requiescens n. igen. n. isp., from the early Permian Tambach Formation at the Bromacker locality, Thuringia, Germany.5 They are the only definite early synapsid-and, more specifically, sphenacodontid-full-body impressions. They include skin impressions of the limbs, trunk, and tail that show epidermal scales and are associated with Dimetropus leisnerianus footprints. Through a morphological comparison with modern taxa,6 we demonstrate for the first time the unequivocal occurrence of epidermal scales in early synapsids. A review of the early amniote and stem amniote trace and body fossil skin record highlights that this constitutes the oldest occurrence of epidermal scales in synapsids, long before the acquisition of hair.7 Moreover, we find the first fossil occurrence of epidermal scales in eight different tetrapod groups during the early Permian. This implies an earlier common origin of epidermal scales. The higher chance of preservation and spreading in the early Permian was probably due to a structural reinforcement of the scales as an adaptation to global warming and aridization8 at the end of the Late Paleozoic Ice Age. Moreover, sphenacodontid resting, swimming, and locomotion traces of multiple individuals of different sizes co-occur on the same bedding planes, in a relatively small area. This is interpreted as the earliest documented aggregation behavior in sphenacodontid synapsids that gathered in and around small ponds.
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Affiliation(s)
- Lorenzo Marchetti
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany.
| | - Antoine Logghe
- Centre de Recherche en Paléontologie - Paris, UMR 7207 - CNRS, MNHN, SU, Muséum National d'Histoire Naturelle, 8 rue Buffon, CP38, Paris, France
| | - Michael Buchwitz
- Museum für Naturkunde Magdeburg, Otto-von-Guericke-Straße 68-73, 39104 Magdeburg, Germany
| | - Jörg Fröbisch
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, 10115 Berlin, Germany; Institut für Biologie, Humboldt-Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany
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Osterling Arias AF, Mooney ED, Bevitt JJ, Reisz RR. A new trematopid from the lower Permian of Oklahoma and new insights into the genus Acheloma. PLoS One 2024; 19:e0309393. [PMID: 39418236 PMCID: PMC11486393 DOI: 10.1371/journal.pone.0309393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Accepted: 08/09/2024] [Indexed: 10/19/2024] Open
Abstract
Modern-day terrestrial amphibians pale in comparison to their monstrous ancient relatives, the Late Carboniferous and Early Permian trematopid temnospondyls. With a skeleton that clearly indicated a terrestrial mode of life and armed with an impressive set of large, recurved marginal dentition and palatal fangs for holding their prey-this group of terrestrial temnospondyls roamed North America and Central Europe as a top predator. Lack of substantial informative fossil material has previously limited our understanding of trematopid diversity and ontogeny. Fortunately, this has improved in the last few decades with the help of exceptional localities like the Early Permian locality Richards Spur. While multiple species of dissorophid temnospondyl have been described from Richards Spur, only one trematopid species has been confidently recognized -Acheloma dunni. Here, we report on the presence of a new large, relatively mature trematopid skull from this famous locality, found encased within a limestone rich block composed mostly of skeletal remains from several other taxa. With the help of neutron computed tomography (nCT), a non-invasive method of analyzing internal and external morphologies, this specimen has revealed several features consistent with the genus, Acheloma, but distinct from Acheloma cumminsi and Acehloma dunni. The identification of these new features, in addition to the characters it shares with other Acheloma species, not only constitute it as a new species of this genus, but also challenges the notion of having synonymized Acheloma dunni with Acheloma cumminsi. In this study, we also unveil new anatomical characters that are potentially independent of ontogeny and could therefore help clarify some of the phylogenetic relationships of this fascinating group of Paleozoic terrestrial predators.
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Affiliation(s)
| | - Ethan D. Mooney
- Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada
- International Center of Future Science, Dinosaur Evolution Research Center, Jilin University, Changchun, Jilin, Peoples Republic of China
| | - Joseph J. Bevitt
- Australian Nuclear and Science Technology Organization (ANSTO), Australian Centre for Neutron Scattering, Lucas Heights, Sydney, New South Wales, Australia
| | - Robert R. Reisz
- Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada
- International Center of Future Science, Dinosaur Evolution Research Center, Jilin University, Changchun, Jilin, Peoples Republic of China
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Voigt S, Calábková G, Ploch I, Nosek V, Pawlak W, Raczyński P, Spindler F, Werneburg R. A diadectid skin impression and its implications for the evolutionary origin of epidermal scales. Biol Lett 2024; 20:20240041. [PMID: 38773928 PMCID: PMC11285442 DOI: 10.1098/rsbl.2024.0041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 03/22/2024] [Accepted: 03/22/2024] [Indexed: 05/24/2024] Open
Abstract
Corneous skin appendages are not only common and diverse in crown-group amniotes but also present in some modern amphibians. This raises the still unresolved question of whether the ability to form corneous skin appendages is an apomorphy of a common ancestor of amphibians and amniotes or evolved independently in both groups. So far, there is no palaeontological contribution to the issue owing to the lack of keratin soft tissue preservation in Palaeozoic anamniotes. New data are provided by a recently discovered ichnofossil specimen from the early Permian of Poland that shows monospecific tetrapod footprints associated with a partial scaly body impression. The traces can be unambiguously attributed to diadectids and are interpreted as the globally first evidence of horned scales in tetrapods close to the origin of amniotes. Taking hitherto little-noticed scaly skin impressions of lepospondyl stem amniotes from the early Permian of Germany into account, the possibility has to be considered that the evolutionary origin of epidermal scales deeply roots among anamniotes.
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Affiliation(s)
- Sebastian Voigt
- Urweltmuseum GEOSKOP, Burgstr. 19, Thallichtenberg66871, Germany
| | - Gabriela Calábková
- Department of Geology and Paleontology, Moravian Museum, Zelný Trh 6,Brno 659 37, Czech Republic
| | - Izabela Ploch
- Polish Geological Institute – National Research Institute, Rakowiecka 4,Warszawa 00-975, Poland
| | - Vojtěch Nosek
- Department of Archaeology and Museology, Faculty of Arts, Masaryk University, Joštova 220/13,Brno 662 43, Czech Republic
| | - Wojciech Pawlak
- Department of Biology, University of Warsaw, Miecznikowa 1,Warszawa 02-089, Poland
| | - Paweł Raczyński
- Institute of Geological Sciences, Wrocław University, Pl. Maksa Borna 9, Wrocław50-204, Poland
| | | | - Ralf Werneburg
- Naturhistorisches Museum Schloss Bertholdsburg Schleusingen, Burgstr. 6,Schleusingen 98553, Germany
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Plikus MV. Ancient skin sported intricately patterned scales. Nature 2024; 627:274-276. [PMID: 38448530 DOI: 10.1038/d41586-024-00587-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2024]
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Marris E. This is the oldest fossilized reptile skin ever found - it pre-dates the dinosaurs. Nature 2024:10.1038/d41586-024-00032-9. [PMID: 38212615 DOI: 10.1038/d41586-024-00032-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
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