The anatomy and functional morphology of Phacops (Trilobita) from the Hunsrück Slate (Devonian)

Bruton, David L.; Haas, Winfried

doi:10.1127/pala/253/1999/29

Cited by 34 publications

(15 citation statements)

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“…The overall morphological organization of the trilobite protopodite has been elusive because of its non-biomineralized nature and proximity to the midline, with three-dimensional structure being especially difficult to reconstruct because of a lack of suitable trilobite fossils that clearly show this structure (Whittington, 1975; Zeng et al, 2017; Holmes et al, 2020; Bicknell et al, 2021; Hou et al, 2021; Siveter et al, 2021). This has left a gap in our understanding of locomotion, enrollment, and feeding autecology because of the crucial role of the protopodite (Bruton and Haas, 1999; Ortega-Hernández and Brena, 2012; Bicknell et al, 2018, 2021). Appendages are most frequently preserved in highly compressed anterior or posterior views such as Olenoides serratus from the Burgess Shale (Whittington, 1975; Hou et al, 2021), Redlichia rex (Holmes et al, 2020) from Emu Bay, or Hongshiyanaspis yiliangensis (Zeng et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…For instance, the cross section the trilobite protopodite has been reconstructed as having disparate shapes, including oval (e.g. Whittington, 1975; Whittington and Almond, 1987; Bruton and Haas, 1999; Ortega-Hernández and Brena, 2012; Bicknell et al, 2021; Schmidt et al, 2021), square (Hou et al, 2021), or this aspect has been omitted them altogether because of the lack of available data (Whittington, 1993).…”

Section: Discussionmentioning

confidence: 99%

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Convergent evolution of ventral adaptations for enrollment in trilobites and extant euarthropods

Losso,

Affatato,

Nanglu

et al. 2023

Preprint

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The ability to enroll for protection is an effective defensive strategy that has convergently evolved multiple times in disparate animal groups ranging from euarthropods to mammals. Enrollment is an evolutionary staple of trilobites, and their biomineralized dorsal exoskeleton offers a versatile substrate for the evolution of interlocking devices. However, it is unknown whether trilobites also featured ventral adaptations for enrolment. Here, we report ventral exoskeletal adaptations that facilitate enrollment in exceptionally preserved trilobites from the Upper Ordovician Walcott-Rust Quarry in New York State, USA. Walcott-Rust trilobites reveal the intricate three-dimensional organization of the non-biomineralized ventral anatomy preserved as calcite casts, including the spatial relationship between the articulated sternites (i.e., ventral exoskeletal plates) and the wedge-shaped protopodites. Enrollment in trilobites is achieved by ventrally dipping the anterior margin of the sternites during trunk flexure, facilitated by the presence of flexible membranes, and the close coupling of the wedge-shaped protopodites. Comparisons with the ventral morphology of extant glomerid millipedes and terrestrial isopods reveal similar mechanisms used for enrollment. The wedge-shaped protopodites of trilobites closely resemble the gnathobasic coxa/protopodite of extant horseshoe crabs. We propose that the trilobites’ wedge-shaped protopodite simultaneously facilitates tight enrollment and gnathobasic feeding with the trunk appendages.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Convergent evolution of ventral adaptations for enrollment in trilobites and extant euarthropods

Losso,

Affatato,

Nanglu

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…The overall morphological organization of the trilobite protopodite has been elusive because of its non-biomineralized nature and proximity to the midline, with its three-dimensional structure being especially difficult to reconstruct because of a lack of suitable trilobite fossils that clearly show this structure [17,20,22,34,45,46]. This has left a gap in our understanding of locomotion, enrolment and feeding autecology because of the crucial role of the protopodite [21,22,30,47].…”

Section: (C) Functional Implications Of Wedge-shaped Protopoditesmentioning

confidence: 99%

“…B 290: 20232212 reconstructed as having disparate shapes, including oval (e.g. [17,19,[21][22][23]30]), square [20], or this aspect has been omitted them altogether because of the lack of available data [14].…”

Section: (C) Functional Implications Of Wedge-shaped Protopoditesmentioning

confidence: 99%

Convergent evolution of ventral adaptations for enrolment in trilobites and extant euarthropods

Losso,

Affatato,

Nanglu

et al. 2023

Proc. R. Soc. B.

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The ability to enrol for protection is an effective defensive strategy that has convergently evolved multiple times in disparate animal groups ranging from euarthropods to mammals. Enrolment is a staple habit of trilobites, and their biomineralized dorsal exoskeleton offered a versatile substrate for the evolution of interlocking devices. However, it is unknown whether trilobites also featured ventral adaptations for enrolment. Here, we report ventral exoskeletal adaptations that facilitate enrolment in exceptionally preserved trilobites from the Middle Ordovician Walcott–Rust Quarry in New York State, USA. Walcott–Rust trilobites reveal the intricate three-dimensional organization of the non-biomineralized ventral anatomy preserved as calcite casts, including the spatial relationship between the articulated sternites (i.e. ventral exoskeletal plates) and the wedge-shaped protopodites. Enrolment in trilobites is achieved by ventrally dipping the anterior margin of the sternites during trunk flexure, facilitated by the presence of flexible membranes, and with the close coupling of the wedge-shaped protopodites. Comparisons with the ventral morphology of extant glomerid millipedes and terrestrial isopods reveal similar mechanisms used for enrolment. The wedge-shaped protopodites of trilobites closely resemble the gnathobasic coxa/protopodite of extant horseshoe crabs. We propose that the trilobites' wedge-shaped protopodite simultaneously facilitated tight enrolment and gnathobasic feeding with the trunk appendages.

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“…The Devonian Phacops ( Chotecops ) sp. from the Hunsrück Slate has ‘bristles’ along the distal margin of its antennal articles (Bruton and Haas, 1999, text-fig. 28a), the morphology and distribution of which are likewise suggestive of trichoid mechanosensory sensilla.…”

Section: Introductionmentioning

confidence: 99%

A novel antennal form in trilobites

Edgecombe

Fortey

2022

J. Paleontol.

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Known antennae of trilobites are all flagelliform, in marked contrast to the varied first antennae of marine pancrustaceans. An exceptionally preserved specimen of the Early Ordovician (late Tremadocian) asaphid Asaphellus tataensis Vidal, 1998, from the Fezouata Shale in Morocco, exhibits both antennae in situ; they are relatively short, widen distally, and bear a series of round, dome-shaped organs along both their dorsal and ventral surfaces. These organs are vastly larger than chemo- or mechanosensory sensilla on the antennae of other arthropods, rendering their homology and function uncertain. The clavate antennae of Asaphellus reveal the furthest deviation from the inferred ancestral state of the trilobite antenna known to date. This could be an adaptation for detection of prey, because most Asaphidae have been claimed as predators and scavengers on the basis of specialized features of the calcified exoskeleton.

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The anatomy and functional morphology of Phacops (Trilobita) from the Hunsrück Slate (Devonian)

Cited by 34 publications

References 0 publications

Convergent evolution of ventral adaptations for enrollment in trilobites and extant euarthropods

Convergent evolution of ventral adaptations for enrollment in trilobites and extant euarthropods

Convergent evolution of ventral adaptations for enrolment in trilobites and extant euarthropods

A novel antennal form in trilobites

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