We have described mandibular specimens of fossil colobines from the late Miocene site of Nakali (Kenya). Using qualitative and quantitative dental and mandibular traits, we compared them to an extensive sample of extant colobines and Miocene fossil colobines. We tested the hypothesis that i) only one species was present in this newly described fossil sample, ii) this species is phenetically distinct from fossil colobines from Ngerngerwa and Ngorora, iii) this species is phenetically distinct from hitherto documented fossil Miocene colobines, and iv) this species is phenetically more different from extant African colobines than from Asian colobines. Bootstrap analyses demonstrated that the Nakali specimens belong to a single fossil species. Dental and symphyseal morphometric ratios and a morphometric geometric analysis of the corpus cross-section showed that the Nakali colobines belong to Microcolobus tugenensis. Bootstrap analyses failed to unambiguously confirm the distinct taxonomic status of isolated dental specimens from Ngerngerwa and Ngorora, and suggest that they may represent, along with the Nakali sample, a single species. A linear discriminant analysis established on dental linear dimensions of four Nakali specimens classified them within the African colobine tribe (Colobini). Microcolobus have a P4 occlusal morphology, a breadth differential of the symphyseal transverse tori, and an inclination of the symphysis similar to extant African colobines. However, the corpus shape of Microcolobus is closer to that of primitive cercopithecoids, in addition to the lack of the diagnostic mesiodistal elongation of the lower canine of extant African colobines, suggesting that Microcolobus is likely a stem Colobinae.
{"title":"Description of new mandibular remains of Microcolobus from Nakali (ca. 10 Ma, Kenya): implications on the evolution of Miocene colobines","authors":"Laurent Pallas, Masato Nakatsukasa, Yutaka Kunimatsu","doi":"10.1101/2024.03.31.587461","DOIUrl":"https://doi.org/10.1101/2024.03.31.587461","url":null,"abstract":"We have described mandibular specimens of fossil colobines from the late Miocene site of Nakali (Kenya). Using qualitative and quantitative dental and mandibular traits, we compared them to an extensive sample of extant colobines and Miocene fossil colobines. We tested the hypothesis that i) only one species was present in this newly described fossil sample, ii) this species is phenetically distinct from fossil colobines from Ngerngerwa and Ngorora, iii) this species is phenetically distinct from hitherto documented fossil Miocene colobines, and iv) this species is phenetically more different from extant African colobines than from Asian colobines. Bootstrap analyses demonstrated that the Nakali specimens belong to a single fossil species. Dental and symphyseal morphometric ratios and a morphometric geometric analysis of the corpus cross-section showed that the Nakali colobines belong to <em>Microcolobus tugenensis</em>. Bootstrap analyses failed to unambiguously confirm the distinct taxonomic status of isolated dental specimens from Ngerngerwa and Ngorora, and suggest that they may represent, along with the Nakali sample, a single species. A linear discriminant analysis established on dental linear dimensions of four Nakali specimens classified them within the African colobine tribe (Colobini). <em>Microcolobus</em> have a P<sub>4</sub> occlusal morphology, a breadth differential of the symphyseal transverse tori, and an inclination of the symphysis similar to extant African colobines. However, the corpus shape of <em>Microcolobus</em> is closer to that of primitive cercopithecoids, in addition to the lack of the diagnostic mesiodistal elongation of the lower canine of extant African colobines, suggesting that <em>Microcolobus</em> is likely a stem Colobinae.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140600652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-28DOI: 10.1101/2024.03.25.586561
Serjoscha W. Evers, Christian Foth, Walter G Joyce, Guilherme Hermanson
Inferring palaeoecology for fossils is a key interest of palaeobiology. For groups with extant representatives, correlations of aspects of body shape with ecology can provide important insights to understanding extinct members of lineages. The origin and ancestral ecology of turtles is debated and various shell or limb proportions have been reported to correlate with habitat ecology among extant turtles, such that they may be informative for inferring the ecology of fossil turtles, including early shelled stem turtles. One recently described method proposes that simple shell measurements that effectively quantify shell doming and plastron width can differentiate habitat classes among extant turtles in linear discriminant analysis, whereby aquatic turtles have low domed shells with narrow plastra. The respective study proposes unorthodox habitat predictions for key fossil turtles, including aquatic lifestyles for the early turtle Proganochelys quenstedtii and the meiolaniform Meiolania platyceps, and terrestrial habits for the early turtle Proterochersis robusta. Here, we show that these published results are the consequence of questionable methodological choices such as omission of species data which do not conform to a preconceived shell shape-ecology association. When these choices are reversed, species measurements for fossils are corrected, and phylogenetic flexible discriminant analysis applied, habitat cannot be correctly predicted for extant turtles based on these simple shell measurements. This invalidates the method as well as the proposed palaeohabitats for fossils.
{"title":"Simple shell measurements do not consistently predict habitat in turtles: a reply to Lichtig and Lucas (2017)","authors":"Serjoscha W. Evers, Christian Foth, Walter G Joyce, Guilherme Hermanson","doi":"10.1101/2024.03.25.586561","DOIUrl":"https://doi.org/10.1101/2024.03.25.586561","url":null,"abstract":"Inferring palaeoecology for fossils is a key interest of palaeobiology. For groups with extant representatives, correlations of aspects of body shape with ecology can provide important insights to understanding extinct members of lineages. The origin and ancestral ecology of turtles is debated and various shell or limb proportions have been reported to correlate with habitat ecology among extant turtles, such that they may be informative for inferring the ecology of fossil turtles, including early shelled stem turtles. One recently described method proposes that simple shell measurements that effectively quantify shell doming and plastron width can differentiate habitat classes among extant turtles in linear discriminant analysis, whereby aquatic turtles have low domed shells with narrow plastra. The respective study proposes unorthodox habitat predictions for key fossil turtles, including aquatic lifestyles for the early turtle Proganochelys quenstedtii and the meiolaniform Meiolania platyceps, and terrestrial habits for the early turtle Proterochersis robusta. Here, we show that these published results are the consequence of questionable methodological choices such as omission of species data which do not conform to a preconceived shell shape-ecology association. When these choices are reversed, species measurements for fossils are corrected, and phylogenetic flexible discriminant analysis applied, habitat cannot be correctly predicted for extant turtles based on these simple shell measurements. This invalidates the method as well as the proposed palaeohabitats for fossils.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"130 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140324336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-19DOI: 10.1101/2024.03.18.585490
Lorenzo Lustri, Jonathan B. Antcliffe, Pierre Gueriau, Allison C. Daley
The rapid early diversification of arthropods has made understanding internal relationships within the group fiendish. Particularly unresolved is the origin of Euchelicerata, a clade consisting of the Prosomapoda (comprising the extant Xiphosura and Arachnida and the extinct Chasmataspidida, Eurypterida and synziphosurines) and the extinct Offacolidae. Here we describe new material of the Silurian ′synziphosurine′ Bunaia woodwardi that reveals previously unknown features of its ventral anatomy: a pair of elongated chelicerae in the prosoma, followed posteriorly by five pairs of biramous appendages, a first pre-abdomen somite bearing a pair of paddle-like uniramous appendages (exopods), and a ventral pretelsonic process. Phylogenetic analyses retrieve B. woodwardi as an Offacolidae closely related to Setapedites abundantis from the early Ordovician Fezouata Biota. An anatomical comparison of the pretelsonic process of B. woodwardi, also present in Setapedites, with the posterior trunk morphologies of other Offacolidae, Habeliida and Vicissicaudata, suggests a possible homologous appendicular origin. This proposed apomorphic character supports a monophyletic Arachnomorpha, formed of Vicissicaudata, Habeliida and Euchelicerata. The establishment of this new homology could help to clarify the highly enigmatic phylogeny at the base of the euchelicerates as well as the sequence of character acquisition during their early evolution.
{"title":"New specimens of Bunaia woodwardi, Clarke 1919 (Euchelicerata): A new member of Offacolidae providing insight supporting the Arachnomorpha","authors":"Lorenzo Lustri, Jonathan B. Antcliffe, Pierre Gueriau, Allison C. Daley","doi":"10.1101/2024.03.18.585490","DOIUrl":"https://doi.org/10.1101/2024.03.18.585490","url":null,"abstract":"The rapid early diversification of arthropods has made understanding internal relationships within the group fiendish. Particularly unresolved is the origin of Euchelicerata, a clade consisting of the Prosomapoda (comprising the extant Xiphosura and Arachnida and the extinct Chasmataspidida, Eurypterida and synziphosurines) and the extinct Offacolidae. Here we describe new material of the Silurian ′synziphosurine′ <em>Bunaia woodwardi</em> that reveals previously unknown features of its ventral anatomy: a pair of elongated chelicerae in the prosoma, followed posteriorly by five pairs of biramous appendages, a first pre-abdomen somite bearing a pair of paddle-like uniramous appendages (exopods), and a ventral pretelsonic process. Phylogenetic analyses retrieve <em>B. woodwardi</em> as an Offacolidae closely related to <em>Setapedites abundantis</em> from the early Ordovician Fezouata Biota. An anatomical comparison of the pretelsonic process of <em>B. woodwardi</em>, also present in <em>Setapedites</em>, with the posterior trunk morphologies of other Offacolidae, Habeliida and Vicissicaudata, suggests a possible homologous appendicular origin. This proposed apomorphic character supports a monophyletic Arachnomorpha, formed of Vicissicaudata, Habeliida and Euchelicerata. The establishment of this new homology could help to clarify the highly enigmatic phylogeny at the base of the euchelicerates as well as the sequence of character acquisition during their early evolution.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140166159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-15DOI: 10.1101/2024.03.14.585031
Konstantina Agiadi, Niklas Hohmann, Elsa Gliozzi, Danae Thivaiou, Francesca Bosellini, Marco Taviani, Giovanni Bianucci, Alberto Collareta, Laurent Londeix, Costanza Faranda, Francesca Bulian, Efterpi Koskeridou, Francesca Lozar, Alan Maria Mancini, Stefano Dominici, Pierre Moissette, Ildefonso Bajo Campos, Enrico Borghi, George Iliopoulos, Assimina Antonarakou, George Kontakiotis, Evangelia Besiou, Stergios D. Zarkogiannis, Mathias Harzhauser, Francisco Javier Sierro, Marta Coll, Iuliana Vasiliev, Angelo Camerlenghi, Daniel Garcia-Castellanos
Understanding deep-time marine biodiversity change under the combined effects of climate and connectivity changes is fundamental for predicting the impacts of modern climate change in semi-enclosed seas. We quantify the Late Miocene-Early Pliocene (11.63-3.6 Ma) taxonomic diversity of the Mediterranean Sea for calcareous nannoplankton, dinocysts, foraminifera, ostracods, corals, molluscs, bryozoans, echinoids, fishes, and marine mammals. During this time, marine biota was affected by global climate cooling and the restriction of the Mediterranean's connection to the Atlantic Ocean that peaked with the Messinian Salinity Crisis. Although the net change in species richness from the Tortonian to the Zanclean varies by group, species turnover is greater than 30% in all cases. The results show clear perturbation already in the pre-evaporitic Messinian (7.25-5.97 Ma), with patterns differing among groups and sub-basins.
{"title":"Late Miocene transformation of Mediterranean Sea biodiversity","authors":"Konstantina Agiadi, Niklas Hohmann, Elsa Gliozzi, Danae Thivaiou, Francesca Bosellini, Marco Taviani, Giovanni Bianucci, Alberto Collareta, Laurent Londeix, Costanza Faranda, Francesca Bulian, Efterpi Koskeridou, Francesca Lozar, Alan Maria Mancini, Stefano Dominici, Pierre Moissette, Ildefonso Bajo Campos, Enrico Borghi, George Iliopoulos, Assimina Antonarakou, George Kontakiotis, Evangelia Besiou, Stergios D. Zarkogiannis, Mathias Harzhauser, Francisco Javier Sierro, Marta Coll, Iuliana Vasiliev, Angelo Camerlenghi, Daniel Garcia-Castellanos","doi":"10.1101/2024.03.14.585031","DOIUrl":"https://doi.org/10.1101/2024.03.14.585031","url":null,"abstract":"Understanding deep-time marine biodiversity change under the combined effects of climate and connectivity changes is fundamental for predicting the impacts of modern climate change in semi-enclosed seas. We quantify the Late Miocene-Early Pliocene (11.63-3.6 Ma) taxonomic diversity of the Mediterranean Sea for calcareous nannoplankton, dinocysts, foraminifera, ostracods, corals, molluscs, bryozoans, echinoids, fishes, and marine mammals. During this time, marine biota was affected by global climate cooling and the restriction of the Mediterranean's connection to the Atlantic Ocean that peaked with the Messinian Salinity Crisis. Although the net change in species richness from the Tortonian to the Zanclean varies by group, species turnover is greater than 30% in all cases. The results show clear perturbation already in the pre-evaporitic Messinian (7.25-5.97 Ma), with patterns differing among groups and sub-basins.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140146338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-13DOI: 10.1101/2024.03.08.584139
Gregor Hans Mathes, Carl Reddin, Wolfgang Kiessling, Gawain S. Antell, Erin E. Saupe, Manuel J. Steinbauer
Aim: To determine the degree to which assemblages of planktonic foraminifera track thermal conditions. Location: The worlds oceans. Time period: The last 700,000 years of glacial-interglacial cycles. Major taxa studied: Planktonic foraminifera. Methods: We investigate assemblage dynamics in planktonic foraminifera in response to temperature changes using a global dataset of Quaternary planktonic foraminifera, together with a coupled Atmosphere Ocean General Circulation Model (AOGCM) at 8,000-year resolution. We use thermal deviance to assess assemblage responses to climate change, defined as the difference between the temperature at a given location and the bio-indicated temperature (i.e., the abundance-weighted average of estimated temperature optima for the species present). Results: Assemblages generally tracked annual mean temperature changes through compositional turnover, but large thermal deviances are evident under certain conditions. The coldest-adapted species persisted in polar regions during warming but were not joined by additional immigrants, resulting in decreased assemblage turnover with warming. The warmest-adapted species persisted in equatorial regions during cooling. Assemblages at mid latitudes closely tracked temperature cooling and showed a modest increase in thermal deviance with warming. Main conclusions: Planktonic foraminiferal assemblages were generally able to track or endure temperature changes: as climate warmed or cooled, bio-indicated temperature also became warmer or cooler, although to a variable degree. At polar sites under warming and at equatorial sites under cooling, the change in temperature predicted from assemblage composition was less than, or even opposite to, expectations based on estimated environmental change. Nevertheless, all species survived the accumulation of thermal deviance-a result that highlights the resilience and inertia of planktonic foraminifera on an assemblage level to the last 700,000 years of climate change, which might be facilitated by broad thermal tolerances or depth shifts.
{"title":"Spatially heterogeneous responses of planktonic foraminifera assemblages over 700,000 years of climate change","authors":"Gregor Hans Mathes, Carl Reddin, Wolfgang Kiessling, Gawain S. Antell, Erin E. Saupe, Manuel J. Steinbauer","doi":"10.1101/2024.03.08.584139","DOIUrl":"https://doi.org/10.1101/2024.03.08.584139","url":null,"abstract":"Aim: To determine the degree to which assemblages of planktonic foraminifera track thermal conditions. Location: The worlds oceans. Time period: The last 700,000 years of glacial-interglacial cycles. Major taxa studied: Planktonic foraminifera. Methods: We investigate assemblage dynamics in planktonic foraminifera in response to temperature changes using a global dataset of Quaternary planktonic foraminifera, together with a coupled Atmosphere Ocean General Circulation Model (AOGCM) at 8,000-year resolution. We use thermal deviance to assess assemblage responses to climate change, defined as the difference between the temperature at a given location and the bio-indicated temperature (i.e., the abundance-weighted average of estimated temperature optima for the species present). Results: Assemblages generally tracked annual mean temperature changes through compositional turnover, but large thermal deviances are evident under certain conditions. The coldest-adapted species persisted in polar regions during warming but were not joined by additional immigrants, resulting in decreased assemblage turnover with warming. The warmest-adapted species persisted in equatorial regions during cooling. Assemblages at mid latitudes closely tracked temperature cooling and showed a modest increase in thermal deviance with warming. Main conclusions: Planktonic foraminiferal assemblages were generally able to track or endure temperature changes: as climate warmed or cooled, bio-indicated temperature also became warmer or cooler, although to a variable degree. At polar sites under warming and at equatorial sites under cooling, the change in temperature predicted from assemblage composition was less than, or even opposite to, expectations based on estimated environmental change. Nevertheless, all species survived the accumulation of thermal deviance-a result that highlights the resilience and inertia of planktonic foraminifera on an assemblage level to the last 700,000 years of climate change, which might be facilitated by broad thermal tolerances or depth shifts.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140129605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-13DOI: 10.1101/2024.03.12.584484
Robert J Brocklehurst, Magdalen Mercado, Kenneth D Angielczyk, Stephanie E Pierce
The 'sprawling-parasagittal' postural transition is a key part of mammalian evolution, associated with sweeping reorganization of the postcranial skeleton in mammals compared to their forebears, the non-mammalian synapsids. However, disputes over forelimb function in fossil synapsids render the precise nature of the 'sprawling-parasagittal' transition controversial. We shed new light on the origins of mammalian posture, using evolutionary adaptive landscapes to integrate 3D humerus shape and functional performance data across a taxonomically comprehensive sample of fossil synapsids and extant comparators. We find that the earliest pelycosaur-grade synapsids had a unique mode of sprawling, intermediate between extant reptiles and monotremes. Subsequent evolution of synapsid humerus form and function showed little evidence of a direct progression from sprawling pelycosaurs to parasagittal mammals. Instead, posture was evolutionarily labile, and the ecological diversification of successive synapsid radiations was accompanied by variation in humerus morphofunctional traits. Further, synapsids frequently evolve towards parasagittal postures, diverging from the reconstructed optimal evolutionary path; the optimal path only aligns with becoming increasingly mammalian in derived cynodonts. We find the earliest support for habitual parasagittal postures in stem therians, implying that synapsids evolved and radiated with distinct forelimb trait combinations for most of their recorded history.
{"title":"Adaptive landscapes unveil the complex evolutionary path to mammalian forelimb function and posture","authors":"Robert J Brocklehurst, Magdalen Mercado, Kenneth D Angielczyk, Stephanie E Pierce","doi":"10.1101/2024.03.12.584484","DOIUrl":"https://doi.org/10.1101/2024.03.12.584484","url":null,"abstract":"The 'sprawling-parasagittal' postural transition is a key part of mammalian evolution, associated with sweeping reorganization of the postcranial skeleton in mammals compared to their forebears, the non-mammalian synapsids. However, disputes over forelimb function in fossil synapsids render the precise nature of the 'sprawling-parasagittal' transition controversial. We shed new light on the origins of mammalian posture, using evolutionary adaptive landscapes to integrate 3D humerus shape and functional performance data across a taxonomically comprehensive sample of fossil synapsids and extant comparators. We find that the earliest pelycosaur-grade synapsids had a unique mode of sprawling, intermediate between extant reptiles and monotremes. Subsequent evolution of synapsid humerus form and function showed little evidence of a direct progression from sprawling pelycosaurs to parasagittal mammals. Instead, posture was evolutionarily labile, and the ecological diversification of successive synapsid radiations was accompanied by variation in humerus morphofunctional traits. Further, synapsids frequently evolve towards parasagittal postures, diverging from the reconstructed optimal evolutionary path; the optimal path only aligns with becoming increasingly mammalian in derived cynodonts. We find the earliest support for habitual parasagittal postures in stem therians, implying that synapsids evolved and radiated with distinct forelimb trait combinations for most of their recorded history.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"288 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140114994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-02DOI: 10.1101/2024.02.27.582391
Nicholas James Strausfeld, Frank Hirth
Cambrian preservation of fossilized tissues provides crucial information about divergent cerebral arrangements amongst stem arthropods. One such genus is Mollisonia, whose clustered appendages beneath a frontal carapace suggest an early chelicerate. Here we apply neuroanatomical, genetic, and developmental analysis to curated fossil data of Mollisonia to demonstrate that instead of a linear organization of seriate parts like in other Cambrian arthropods, the Mollisonia brain is folded back over segmental ganglia of the prosoma, an organization characterizing the brains of all modern arachnids. The unexpectedly early acquisition of this apomorphic character state demonstrates the divergence of marine Arachnida represented by Mollisonia from Merostomata (horseshoe crabs) and its sister group Pycnogonida (sea spiders), both of which have linearly organized cerebra. While fossil evidence supports a marine origin of total group Chelicerata, we show Mollisoniidae defining the base of the arachnid tree of life that excludes Merostomata and Pycnogonida.
{"title":"Marine Origin of the Arachnid Brain Reveals Early Divergence of Chelicerata","authors":"Nicholas James Strausfeld, Frank Hirth","doi":"10.1101/2024.02.27.582391","DOIUrl":"https://doi.org/10.1101/2024.02.27.582391","url":null,"abstract":"Cambrian preservation of fossilized tissues provides crucial information about divergent cerebral arrangements amongst stem arthropods. One such genus is Mollisonia, whose clustered appendages beneath a frontal carapace suggest an early chelicerate. Here we apply neuroanatomical, genetic, and developmental analysis to curated fossil data of Mollisonia to demonstrate that instead of a linear organization of seriate parts like in other Cambrian arthropods, the Mollisonia brain is folded back over segmental ganglia of the prosoma, an organization characterizing the brains of all modern arachnids. The unexpectedly early acquisition of this apomorphic character state demonstrates the divergence of marine Arachnida represented by Mollisonia from Merostomata (horseshoe crabs) and its sister group Pycnogonida (sea spiders), both of which have linearly organized cerebra. While fossil evidence supports a marine origin of total group Chelicerata, we show Mollisoniidae defining the base of the arachnid tree of life that excludes Merostomata and Pycnogonida.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"78 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140017077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-02DOI: 10.1101/2024.02.29.582715
Thomas A Puschel, Samuel L Nicholson, Joanna Baker, Robert A Barton, Chris Venditti
The fact that rapid brain size increase was clearly a key aspect of human evolution has prompted many studies focussing on this phenomenon, and many suggestions as to the underlying evolutionary patterns and processes. No study to date has however separated out the contributions of change through time within- vs. between- hominin species whilst simultaneously incorporating effects of body size. Using a phylogenetic approach never applied before to palaeoanthropological data, we show that brain size increase across ~ 7 million years of hominin evolution arose from increases within individual species which account for an observed overall increase in relative brain size. Variation among species in brain size after accounting for this effect is associated with body mass differences but not time. In addition, our analysis also reveals that the within-species trend escalated in more recent lineages, implying an overall pattern of accelerating brain size increase through time.
{"title":"Hominin brain size increase has emerged from within-species encephalization","authors":"Thomas A Puschel, Samuel L Nicholson, Joanna Baker, Robert A Barton, Chris Venditti","doi":"10.1101/2024.02.29.582715","DOIUrl":"https://doi.org/10.1101/2024.02.29.582715","url":null,"abstract":"The fact that rapid brain size increase was clearly a key aspect of human evolution has prompted many studies focussing on this phenomenon, and many suggestions as to the underlying evolutionary patterns and processes. No study to date has however separated out the contributions of change through time within- vs. between- hominin species whilst simultaneously incorporating effects of body size. Using a phylogenetic approach never applied before to palaeoanthropological data, we show that brain size increase across ~ 7 million years of hominin evolution arose from increases within individual species which account for an observed overall increase in relative brain size. Variation among species in brain size after accounting for this effect is associated with body mass differences but not time. In addition, our analysis also reveals that the within-species trend escalated in more recent lineages, implying an overall pattern of accelerating brain size increase through time.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"259 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140017116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-29DOI: 10.1101/2024.02.21.581465
Michelle Álvarez Rodríguez, Francisco Riquelme, Miguel A. Hernández Patricio, Fabio Cupul-Magaña
We present a comprehensive catalog with an updated database of the fossil record of Diplopoda in the world. Taxonomic data was collected from descriptions and reports published from 1854 to the present. We also include new records from the Lower Miocene Mexican amber, counting 83 unknown fossil inclusions, with the first records of the orders Polyxenida, Platydesmida, and Julida, as well as the families Sphaeriodesmidae and Trichopolydesmidae within Polydesmida. According to our results, Diplopoda comprises 217 fossil records from the Middle Silurian to Upper Pleistocene, representing three subclasses, six superorders, 25 orders, one superfamily, 54 families, 90 genera, and 156 fossil species. To date, no fossils of the order Siphonocryptida have been reported. The fossil record extends over three geological eras: the Paleozoic, with 156 records; the Mesozoic, with 51; and the Cenozoic, with 77. The fossil preservation includes 87 impressions, 68 compressions, 108 amber inclusions, and 19 ichnites. Thus, this catalog allows us to estimate the size and taxonomic composition of Diplopoda in the fossil record worldwide.
{"title":"Diplopoda in the world fossil record","authors":"Michelle Álvarez Rodríguez, Francisco Riquelme, Miguel A. Hernández Patricio, Fabio Cupul-Magaña","doi":"10.1101/2024.02.21.581465","DOIUrl":"https://doi.org/10.1101/2024.02.21.581465","url":null,"abstract":"We present a comprehensive catalog with an updated database of the fossil record of Diplopoda in the world. Taxonomic data was collected from descriptions and reports published from 1854 to the present. We also include new records from the Lower Miocene Mexican amber, counting 83 unknown fossil inclusions, with the first records of the orders Polyxenida, Platydesmida, and Julida, as well as the families Sphaeriodesmidae and Trichopolydesmidae within Polydesmida. According to our results, Diplopoda comprises 217 fossil records from the Middle Silurian to Upper Pleistocene, representing three subclasses, six superorders, 25 orders, one superfamily, 54 families, 90 genera, and 156 fossil species. To date, no fossils of the order Siphonocryptida have been reported. The fossil record extends over three geological eras: the Paleozoic, with 156 records; the Mesozoic, with 51; and the Cenozoic, with 77. The fossil preservation includes 87 impressions, 68 compressions, 108 amber inclusions, and 19 ichnites. Thus, this catalog allows us to estimate the size and taxonomic composition of Diplopoda in the fossil record worldwide.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"135 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140004186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-21DOI: 10.1101/2024.02.19.580992
Nora Corthesy, Farid Saleh, Camille Thomas, Jonathan B. Antcliffe, Allison C. Daley
Fossilization, or the transition of an organism from the biosphere to the geosphere, is a complex mechanism involving numerous biological and geological variables. Bacteria are one of the most significant biotic players to decompose organic matter in natural environments, early on during fossilization. However, bacterial processes are difficult to characterize as many different abiotic conditions can influence bacterial efficiency in degrading tissues. One potentially important variable is the composition and nature of the sediment on which a carcass is deposited after death. We experimentally examined this by decaying the marine shrimp Palaemon varians underwater on three different clay sediments. Samples were then analyzed using 16S ribosomal RNA sequencing to identify the bacterial communities associated with each clay system. Results show that samples decaying on the surface of kaolinite have a lower bacterial diversity than those decaying on the surface of bentonite and montmorillonite, which could explain the limited decay of carcasses deposited on this clay. However, this is not the only role played by kaolinite, as a greater proportion of gram-negative over gram-positive bacteria is observed in this system. Gram-positive bacteria are generally thought to be more efficient at recycling complex polysaccharides such as those forming the body walls of arthropods. This is the first experimental evidence of sediments shaping an entire bacterial community. Such interaction between sediments and bacteria might have contributed to arthropods' exquisite preservation and prevalence in kaolinite-rich Lagerstatten of the Cambrian Explosion.
{"title":"The effects of clay minerals on bacterial community composition during arthropod decay","authors":"Nora Corthesy, Farid Saleh, Camille Thomas, Jonathan B. Antcliffe, Allison C. Daley","doi":"10.1101/2024.02.19.580992","DOIUrl":"https://doi.org/10.1101/2024.02.19.580992","url":null,"abstract":"Fossilization, or the transition of an organism from the biosphere to the geosphere, is a complex mechanism involving numerous biological and geological variables. Bacteria are one of the most significant biotic players to decompose organic matter in natural environments, early on during fossilization. However, bacterial processes are difficult to characterize as many different abiotic conditions can influence bacterial efficiency in degrading tissues. One potentially important variable is the composition and nature of the sediment on which a carcass is deposited after death. We experimentally examined this by decaying the marine shrimp Palaemon varians underwater on three different clay sediments. Samples were then analyzed using 16S ribosomal RNA sequencing to identify the bacterial communities associated with each clay system. Results show that samples decaying on the surface of kaolinite have a lower bacterial diversity than those decaying on the surface of bentonite and montmorillonite, which could explain the limited decay of carcasses deposited on this clay. However, this is not the only role played by kaolinite, as a greater proportion of gram-negative over gram-positive bacteria is observed in this system. Gram-positive bacteria are generally thought to be more efficient at recycling complex polysaccharides such as those forming the body walls of arthropods. This is the first experimental evidence of sediments shaping an entire bacterial community. Such interaction between sediments and bacteria might have contributed to arthropods' exquisite preservation and prevalence in kaolinite-rich Lagerstatten of the Cambrian Explosion.","PeriodicalId":501477,"journal":{"name":"bioRxiv - Paleontology","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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