Key characters uniting hemichordates and chordates: homologies or homoplasies?

2005 ◽  
Vol 83 (1) ◽  
pp. 8-23 ◽  
Author(s):  
Edward E Ruppert
Keyword(s):  
Functional Morphology ◽  
Nerve Cord ◽  
Cladistic Analysis ◽  
Genetic Data ◽  
Comparative Morphology ◽  
Common Pattern ◽  
Apparent Lack ◽  
Unique Pair ◽  
Organ Level ◽  
Key Characters

Four chordate characters — dorsal hollow nerve cord, notochord, gill slits, and endostyle — are compared morphologically, molecularly, and functionally with similar structures in hemichordates to assess their putative homologies. The dorsal hollow nerve cord and enteropneust neurocord are probably homoplasies. The neurocord (= collar cord) may be an autapomorphy of Enteropneusta that innervates a unique pair of muscles, the perihemal coelomic muscles. Despite the apparent lack of organ-level homology, chordates and enteropneusts share a common pattern of neurulation that preserves a "contact innervation" between neuro- and myo-epithelia, which may be the primitive deuterostome pattern of neuromuscular innervation. The chordate notochord and hemichordate stomochord are probably homoplasies. Other potential notochord antecedents in hemichordates are examined, but no clear homolog is identified. The comparative morphology of notochords suggests that the "stack-of-coins" developmental stage, retained into adulthood only by cephalochordates, is the plesiomorphic notochord form. Hemichordate and chordate gill slits are probably homologs, but only at the level of simple ciliated circular or oval pores, lacking a skeleton, as occur in adults of Cephalodiscus spp., developmentally in some enteropneusts, and in many urochordates. Functional morphology, I125-binding experiments, and genetic data suggest that endostylar function may reside in the entire pharyngeal lining of Enteropneusta and is not restricted to a specialized midline structure as in chordates. A cladistic analysis of Deuterostomia, based partly on homologs discussed in this paper, indicates a sister-taxon relationship between Urochordata and Vertebrata, with Cephalochordata as the plesiomorphic clade.

scholarly journals The Dakoticancridae (Decapoda, Brachyura) from the Late Cretaceous of North America and Mexico

1998 ◽  
Vol 67 (4) ◽  
pp. 237-255 ◽  
Author(s):  
G.A. Bishop ◽  
R.M. Feldmann ◽  
F. Vega
Keyword(s):  
North America ◽  
Functional Morphology ◽  
Late Cretaceous ◽  
Cladistic Analysis ◽  
Low Level ◽  
The Family

The podotrematous crab family Dakoticancridae includes four genera: Dakoticancer Rathbun, Tetracarcinus Weller, Avitelmessus Rathbun, and Seorsus Bishop, all known solely from the Late Cretaceous of North America. Lathelicocarcinus Bishop, originally referred to the family, must be reassigned. Fine details of anatomy, preserved on specimens of D. overanus Rathbun and A. grapsoideus Rathbun, permit description of genital openings and interpretation of functional morphology of appendages. Although one species, D. australis Rathbun, has been found associated with burrow structures, all were probably vagrant epifaunal animals on fine- to medium-grained siliciclastic substrata. Food was probably obtained by generalized low-level predation and scavenging. Results of a cladistic analysis are consistent with the stratigraphic data suggesting that T. subquadrata Weller is nearest the rootstock of the family and that other taxa within the family are derived from it.

The ovipositor system of Scelionid and Platygastrid wasps (Hymenoptera: Platygastroidea): Comparative morphology and phylogenetic implications

1997 ◽  
Vol 11 (1) ◽  
pp. 1 ◽  
Author(s):  
A. D. Austin ◽  
and S. A. Field
Keyword(s):  
Cladistic Analysis ◽  
Type System ◽  
Comparative Morphology ◽  
Morphological Characters ◽  
Sensu Stricto ◽  
Ground Plan ◽  
Phylogenetic Implications ◽  
The Status ◽  
Baseline Information

The morphology of the sclerotised components of the ovipositor system is comprehensively surveyed for scelionid and platygastrid wasps, with information being assessed for 120 genera and 220 species. A diagnosis for the ovipositor system is presented for most genera to complement existing generic descriptions. Two previously described and mechanically different forms of the ovipositor system are recognised: (1) the Ceratobaeus-type that is extended and retracted by antagonistic muscles and (2) the Scelio-type that is operated by changes in hydrostatic pressure, where the ovipositor is extended at the end of an elongate telescopic tube derived from expanded intersegmental membrane between metasomal segments 6 and 7. Comparison of these forms with the supposed ground plan for the Scelionidae strongly indicates that the Scelio-type is apomorphic, that it defines a monophyletic group associated with orthopteran host eggs, and that it comprises the tribes Scelionini, Calliscelionini, most Psilanteridini, Aradophagini, Neoscelionini, Platyscelionini, Doddiellini and four genera misplaced within the Sparasionini and Baryconini (Archaeoteleia Masner, Bracalba Dodd, Chromoteleia Ashmead and Oxyscelio Kieffer), as well as Sceliacanthella Dodd. Until a more robust classification of the superfamily is forthcoming, it is proposed that this group be informally referred to as the 'Scelionini sensu lato'. Further, seven genera (Habroteleia Kieffer, Palpoteleia Kieffer, Anteris Foerster, Fusicornia Risbec, Leptoteleia Kieffer, Opisthacantha Ashmead and Styloteleia Kieffer) are misplaced in the Calliscelionini and Psilanteridini because they possess the Ceratobaeus-type system. Nixonia Masner, Sparasion Latreille and Sceliomorpha Ashmead (Sparasionini) are considered to have the most primitive ovipositor system because they possess a Ceratobaeus-type system, and sub-basally fused lateral and latero-ventral apodemes, the latter being loosely attached to sternite 6. Sparasion and Sceliomorpha also have very short lateral apodemes and this, in conjunction with the form of the apodemes, can be considered to be the ground plan for the superfamily. The Platygastridae all possess a modified ovipositor system but, nonetheless, one that in most cases is extended and retracted by musculature (i.e. Ceratobaeus-type). In particular, the system in most platygastrids is typified by having metasomal tergite 8 and associated cerci missing, the lateral apodemes short and forming a U-shape, and the ovipositor assembly generally robust. Only one of approximately 30 genera examined, Acerotella Masner, has very elongate apodemes, as in the Scelionidae. Many platygastrids also have a pair of latero-ventral apodemes, a presumed plesiomorphic character, rather than a single medial apodeme on stemite 6, which is the case for many Scelionidae. The most highly modified system is found in Isostasius Foerster and some Synopeas (Sactogaster) Foerster, where the ovipositor assembly is coiled vertically or partly so and the apodemes are greatly reduced. Generally, characters associated with the ovipositor system do not provide any independent support for the most recent higher-level classification of platygastrids, although they show substantial potential for more accurate definition of genera. A preliminary cladistic analysis of 14 ovipositor characters supports the monophyly of five clades that correspond to the Scelionini s. l., the Scelionidae (minus the Sparasionini sensu stricto), the Sparasionini s. str., the Platygastridae, and the Sparasioriini s. str. + Platygastridae. Overall, results from this study will provide baseline information on the ovipositor system as a prelude to a more complete phylogenetic analysis of the superfamily including external morphological characters. Although no new classification for the Scelionidae and Platygastridae is proposed, their higher-level taxonomy is reviewed and discussed and cases identified where, on the basis of ovipositor morphology, taxa (tribes and/or genera) apparently form monophyletic groups, and where taxa are misplaced. Finally, the status of the major higher-level groups within the superfamily is discussed, as is the available evidence to support their monophyly.

scholarly journals Hierarchical Structure of the Cocos nucifera (Coconut) Endocarp: Functional Morphology and its Influence on Fracture Toughness

Molecules ◽  
2020 ◽  
Vol 25 (1) ◽  
pp. 223 ◽  
Author(s):  
Stefanie Schmier ◽  
Naoe Hosoda ◽  
Thomas Speck
Keyword(s):  
Fracture Toughness ◽  
Functional Morphology ◽  
Role Models ◽  
Imaging Techniques ◽  
Cocos Nucifera ◽  
Hierarchical Level ◽  
Special Focus ◽  
Toughening Mechanisms ◽  
Hierarchical Levels ◽  
Organ Level

In recent years, the biomimetic potential of lignified or partially lignified fruit pericarps has moved into focus. For the transfer of functional principles into biomimetic applications, a profound understanding of the structural composition of the role models is important. The aim of this study was to qualitatively analyze and visualize the functional morphology of the coconut endocarp on several hierarchical levels, and to use these findings for a more precise evaluation of the toughening mechanisms in the endocarp. Eight hierarchical levels of the ripe coconut fruit were identified using different imaging techniques, including light and scanning electron microscopy as well as micro-computer-tomography. These range from the organ level of the fruit (H0) to the molecular composition (H7) of the endocarp components. A special focus was laid on the hierarchical levels of the endocarp (H3–H6). This investigation confirmed that all hierarchical levels influence the crack development in different ways and thus contribute to the pronounced fracture toughness of the coconut endocarp. By providing relevant morphological parameters at each hierarchical level with the associated toughening mechanisms, this lays the basis for transferring those properties into biomimetic technical applications.

Morphology supports ­the setaphyte hypothesis: mosses plus liverworts form a natural group

2018 ◽  
Vol 40 (2) ◽  
pp. 11 ◽  
Author(s):  
KAREN S. RENZAGLIA ◽  
JUAN CARLOS VILLARREAL AGUILAR ◽  
DAVID J. GARBARY
Keyword(s):  
Evolutionary Biology ◽  
Food Source ◽  
Cladistic Analysis ◽  
Genetic Data ◽  
Land Plants ◽  
Taxon Sampling ◽  
Natural Group ◽  
Early Diversification ◽  
Terrestrial Life ◽  
Fundamental Conclusion

The origin and early diversification of land plants is one of the major unresolved problems in evolutionary biology. Occurring nearly half a billion years ago, the transmigration of green organisms to land changed the landscape and provided the food source for terrestrial life to invade a vast uninhabited space, adapt and radiate. Although bryophytes (mosses, liverworts and hornworts) are often regarded as the earliest terrestrial organisms, the order of their divergence remains contentious even as molecular analyses become more conclusive with expanded taxon sampling, massive genetic data and more sophisticated methods of analysis (Cox et al. 2018; Morris et al. 2018). Indeed, virtually every combination of relationships among bryophytes has been proposed based on molecules (Qiu et al. 2006; Wickett et al. 2014; Cox et al. 2018). Fortunately, in 2018 it appears that we are approaching a consensus based on molecules, and that is that although bryophytes may or may not be monophyletic, mosses plus liverworts form a natural group (Puttick et al. 2018). In this essay, we point out that this inference is neither new nor surprising as it has been the fundamental conclusion of morphological analyses for over 25 years starting with an exhaustive cladistic analysis of characters associated with motile cell development in green plants (Garbary et al. 1993).

scholarly journals Boolean logic and character state identity: pitfalls of character coding in metazoan cladistics

2002 ◽  
Vol 71 (1-3) ◽  
pp. 67-91 ◽  
Author(s):  
Ronald A. Jenner
Keyword(s):  
Cladistic Analysis ◽  
Comparative Morphology ◽  
Boolean Logic ◽  
Morphological Data ◽  
Critical Study ◽  
Published Data ◽  
Character State ◽  
Data Sets ◽  
State Identity ◽  
Character Coding

A critical study of the morphological data sets used for the most recent analyses of metazoan cladistics exposes a rather cavalier attitude towards character coding. Binary absence/presence coding is ubiquitous, but without any explicit justification. This uncompromising application of Boolean logic in character coding is remarkable since several recent investigations have nominated absence/presence coding as the most problematic coding method available for standard cladistic analysis. Moreover, the prevalence of unspecified “absence” character states in the published data sets introduces a discrepancy between the theoretical foundations of phylogenetic parsimony and current practices in metazoan cladistics. Because phylogenetic parsimony assumes transformation of character states, its effective operation breaks down when not all character states are carefully delimited. Examples of resulting meaningless character state transformations are discussed in two categories: 1) when unspecified “absence” states are plesiomorphic; and 2) when unspecified “absence” states are apomorphic (character reversals). To facilitate future progress in metazoan cladistics, the mandatory link between comparative morphology and character coding needs to be reestablished through a more explicit study of morphological variation prior to character coding, and through a more explicitly experimental approach to character coding.

scholarly journals The origin and evolution of chordate nervous systems

2015 ◽  
Vol 370 (1684) ◽  
pp. 20150048 ◽  
Author(s):  
Linda Z. Holland
Keyword(s):  
Neural Crest ◽  
Nerve Cord ◽  
Comparative Morphology ◽  
Nervous Systems ◽  
Origin And Evolution ◽  
Developmental Gene Expression ◽  
Vertebrate Brain ◽  
Genome Duplications ◽  
Mechanisms Of Development ◽  
Minority View

In the past 40 years, comparisons of developmental gene expression and mechanisms of development (evodevo) joined comparative morphology as tools for reconstructing long-extinct ancestral forms. Unfortunately, both approaches typically give congruent answers only with closely related organisms. Chordate nervous systems are good examples. Classical studies alone left open whether the vertebrate brain was a new structure or evolved from the anterior end of an ancestral nerve cord like that of modern amphioxus. Evodevo plus electron microscopy showed that the amphioxus brain has a diencephalic forebrain, small midbrain, hindbrain and spinal cord with parts of the genetic mechanisms for the midbrain/hindbrain boundary, zona limitans intrathalamica and neural crest. Evodevo also showed how extra genes resulting from whole-genome duplications in vertebrates facilitated evolution of new structures like neural crest. Understanding how the chordate central nervous system (CNS) evolved from that of the ancestral deuterostome has been truly challenging. The majority view is that this ancestor had a CNS with a brain that gave rise to the chordate CNS and, with loss of a discrete brain, to one of the two hemichordate nerve cords. The minority view is that this ancestor had no nerve cord; those in chordates and hemichordates evolved independently. New techniques such as phylostratigraphy may help resolve this conundrum.

The comparative morphology, phylogeny and evolution of the gastropod family littorinidae

1989 ◽  
Vol 324 (1220) ◽  
pp. 1-110 ◽  
Keyword(s):  
Phylogenetic Relationships ◽  
Maximum Parsimony ◽  
Cladistic Analysis ◽  
Comparative Morphology ◽  
Phylogenetic Significance ◽  
Consensus Tree ◽  
Organ Systems ◽  
The Family ◽  
Phylogeny And Evolution ◽  
Principle Of Maximum

An account is given of the comparative morphology of the family Littorinidae, based on examination of 122 species, grouped into 32 subgenera. The shell, operculum and principal organ systems are described, and their phylogenetic significance assessed. A total of 53 characters, coded as 131 character states, were chosen for inclusion in a cladistic analysis of the phylogenetic relationships of the subgenera. This was performed by the program paup, using the principle of maximum parsimony. The outgroup for the analysis comprised representatives of the Pomatiasidae and Skeneopsidae. A consensus tree was obtained from cladograms with consistency indices of 0.408 (autapomorphies excluded).

scholarly journals Taxonomic revision ofEoalligator(Crocodylia, Brevirostres) and the paleogeographic origins of the Chinese alligatoroids

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2356 ◽  
Author(s):  
Yan-yin Wang ◽  
Corwin Sullivan ◽  
Jun Liu
Keyword(s):  
Phylogenetic Analysis ◽  
Type Species ◽  
New Genus ◽  
Cladistic Analysis ◽  
Guangdong Province ◽  
Taxonomic Revision ◽  
Phylogenetic Position ◽  
Crucial Step ◽  
Alligator Sinensis ◽  
Key Characters

Background.The primarily Neotropical distribution of living alligatoroids raises questions as to when and how the ancestors ofAlligator sinensismigrated to China. As phylogeny provides a necessary framework for historical biogeographic issues, determining the phylogenetic positions of the Chinese alligatoroids is a crucial step towards understanding global alligatoroid paleobiogeography. Besides the unnamed alligatoroids from the Eocene of Guangdong Province, three Chinese fossil taxa have been referred to Alligatoroidea:Alligator luicus,Eoalligator chunyiiandEoalligator huiningensis. However, none of these fossil taxa has been included in a phylogenetic analysis. The genusEoalligatorwas established to accommodateE. chunyiifrom Guangdong Province.E. huiningensisfrom Anhui Province was later erected as a second species, despite no distinctive similarities withE. chunyii. By contrast, the putative crocodylineAsiatosuchus nanlingensiswas established based on material from Guangdong Province, close to theE. chunyiispecimens geographically and stratigraphically. Furthermore, specimens ofA. nanlingensisandE. chunyiishare four distinctive characters, but display no evident differences. As a result, the taxonomic relationships of these three species require restudy.Methods.In this paper, all specimens ofE. chunyiiandE. huiningensisare reassessed in detail, and compared to specimens ofA. nanlingensis. Detailed re-descriptions and revised diagnoses are provided, and a cladistic analysis is carried out to assess the phylogenetic positions ofE. chunyii,E. huiningensisandA. nanlingensis.Results.The analysis recoversE. chunyiiandA. nanlingensisas sister taxa among basal Crocodylidae, whileP. huiningensisis posited as an alligatoroid. Two key characters support the monophylyE. chunyii+A. nanlingensis: sulcus within surangular, and anteroposteriorly oriented surangular-articular suture. The former character is unique toE. chunyiiandA. nanlingensisamong crocodyloids, although a smaller and more posteriorly positioned surangular fossa is known inDiplocynodon. Detailed comparisons show the two species to be synonymous, withE. chunyiias the junior synonym ofA. nanlingensisbased on page priority. BecauseE. chunyiiwas erected as the type species ofEoalligator, the genus is now invalid. We establish the new genusProtoalligatorto accommodate “Eoalligator”huiningensis, an alligatoroid whose exact phylogenetic position is uncertain. In particular,P. huiningensisretains primitive characters such as a lacrimal that extends further anteriorly than the prefrontal, and a notch at the premaxilla-maxilla suture. However,P. huiningensisalso appears to share one important derived character, a complete nasal bar, with alligators. Our taxonomic revisions imply that four alligatoroids are currently known from China, and these species must have dispersed from North America to Asia in more than one event.

Carpals

2020 ◽  
pp. 99-105
Author(s):  
Matthew W. Tocheri ◽  
Job Kibii
Keyword(s):  
Functional Morphology ◽  
Southern Africa ◽  
Comparative Morphology ◽  
Carpal Bones ◽  
Geographical Region ◽  
Modern Humans ◽  
Extreme Caution ◽  
Australopithecus Africanus ◽  
Hominin Evolution ◽  
Fossil Hominin

A capitate and scaphoid are the only carpal bones known from Sterkfontein, and are described here. These bones lack the derived features that characterize the wrist of modern humans and Neandertals solely on the geological and paleontological context of where these specimens were recovered. These elements are attributed to Australopithecus africanus because of where they were recovered, but recent discoveries of A. sediba and Homo naledi from the same geographical region underscore the complexity and diversity of hominin evolution in southern Africa throughout the Pleistocene and suggest extreme caution is needed in attributing isolated hominin elements to particular taxa. Functional interpretations based on single fossil carpals also must be treated cautiously until more reasonably complete fossil hominin hand skeletons are recovered. That said, however, the comparative morphology of these bones suggests that they belonged to hominins in which hand functional morphology was likely broadly similar to that of other early hominins, such as australopiths and Homo floresiensis.

scholarly journals 3D Digitization in Functional Morphology: Where is the Point of Diminishing Returns?

2019 ◽  
Vol 59 (3) ◽  
pp. 656-668 ◽  
Author(s):  
Sharlene E Santana ◽  
Jessica H Arbour ◽  
Abigail A Curtis ◽  
Kathryn E Stanchak
Keyword(s):  
Functional Morphology ◽  
Three Dimensional ◽  
Comparative Morphology ◽  
Micro Computed Tomography ◽  
Evolutionary Patterns ◽  
Geometric Morphometric ◽  
Critical Dimensions ◽  
Contrast Enhanced Ct ◽  
2D Data ◽  
3D Digitization

Abstract Modern computational and imaging methods are revolutionizing the fields of comparative morphology, biomechanics, and ecomorphology. In particular, imaging tools such as X-ray micro computed tomography (µCT) and diffusible iodine-based contrast enhanced CT allow observing and measuring small and/or otherwise inaccessible anatomical structures, and creating highly accurate three-dimensional (3D) renditions that can be used in biomechanical modeling and tests of functional or evolutionary hypotheses. But, do the larger datasets generated through 3D digitization always confer greater power to uncover functional or evolutionary patterns, when compared with more traditional methodologies? And, if so, why? Here, we contrast the advantages and challenges of using data generated via (3D) CT methods versus more traditional (2D) approaches in the study of skull macroevolution and feeding functional morphology in bats. First, we test for the effect of dimensionality and landmark number on inferences of adaptive shifts during cranial evolution by contrasting results from 3D versus 2D geometric morphometric datasets of bat crania. We find sharp differences between results generated from the 3D versus some of the 2D datasets (xy, yz, ventral, and frontal), which appear to be primarily driven by the loss of critical dimensions of morphological variation rather than number of landmarks. Second, we examine differences in accuracy and precision among 2D and 3D predictive models of bite force by comparing three skull lever models that differ in the sources of skull and muscle anatomical data. We find that a 3D model that relies on skull µCT scans and muscle data partly derived from diceCT is slightly more accurate than models based on skull photographs or skull µCT and muscle data fully derived from dissections. However, the benefit of using the diceCT-informed model is modest given the effort it currently takes to virtually dissect muscles from CT scans. By contrasting traditional and modern tools, we illustrate when and why 3D datasets may be preferable over 2D data, and vice versa, and how different methodologies can complement each other in comparative analyses of morphological function and evolution.

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