Could the asymmetrical commissure in rhynchonellide brachiopods be an adaptive trait?

Berrocal-Casero, Mélani; Joral, Fernando García

doi:10.18261/let.56.1.2

Cited by 2 publications

(2 citation statements)

References 26 publications

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“…Although the paleoenvironment in the previously mentioned scenario and those that induced the asymmetry in C. ementitum precursors were different, the physiological response may have been common in both cases, related to the origin of the asymmetry. According to Berrocal-Casero and García Joral (2023), starting from the morphogenetic plasticity of the anterior commissure present in some lineages of rhynchonellides, different palaeoenviromental factors could lead the lophophore to works in an asymmetric way because the water currents enter in the shell preferentially by only one of the two sides. This could have occurred in response to limitations in vital space for living in closely packed clusters; to prevailing or unidirectional currents as usual in reefal or para-reefal environments; and/or to living on soft substrates.…”

Section: Cyclothyris Ementitum and The Obli-gate Type Of Asymmetrymentioning

confidence: 99%

“…The common physiological response in these different scenarios seems to be the differential growth of the lophophore arms, which can lead to external asymmetry. The selection by adaptation of this asymmetry and its genetic assimilation would suppose the fixation of this trait giving rise to the obligate type of asymmetry, which could appear even when the palaeoenvironmental conditions are different to those that induced the adaptation (Berrocal-Casero et al, 2020b, Berrocal-Casero & García Joral, 2023, fig. 7).…”

Section: Cyclothyris Ementitum and The Obli-gate Type Of Asymmetrymentioning

confidence: 99%

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A new asymmetric rhynchonellide from the Cretaceous of the Eastern Prebetic (Southeastern Spain)

Berrocal-Casero

Baeza-Carratalá

Joral

2023

Spanish J. Palaeontol.

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The rhynchonellide genus Cyclothyris M'Coy, 1844, is well represented in the Cretaceous of Europe (e.g., Owen, 1988). Nevertheless, the correct taxonomical classification, and therefore the stratigraphical range and the geographical distribution, of asymmetrical Upper Cretaceous species of Cyclothyris was very confusing until a few years ago, when the asymmetric forms of this genus were updated. This was the result of an intensive revision of numerous specimens of Cyclothyris stored in historical collections from Europe and Northern Africa (e.g., d'Orbigny and Coquand Collections, among others) and also the description of new species (Berrocal-Casero, 2020;Berrocal-Casero et al., 2020a, 2020b. For this previous research, it was essential to distinguish between the terms proposed by Fürsich and Palmer (1984) as 'facultative' type of asymmetry of the anterior commissure, in which the individuals of the same species can develop both symmetric and asymmetric shells [e.g., the Cenomanian Cyclothyris difformis (Valenciennes in Lamarck, 1819

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Section: Cyclothyris Ementitum and The Obli-gate Type Of Asymmetrymentioning

confidence: 99%

Section: Cyclothyris Ementitum and The Obli-gate Type Of Asymmetrymentioning

confidence: 99%

A new asymmetric rhynchonellide from the Cretaceous of the Eastern Prebetic (Southeastern Spain)

Berrocal-Casero

Baeza-Carratalá

Joral

2023

Spanish J. Palaeontol.

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Shell asymmetry in Cretaceous Cyclothyrididae (Brachiopoda): variability, ontogeny and terminology

GASPARD,

PACCARD,

BARDIN

2024

Comptes Rendus Palevol

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The asymmetry observed in rhynchonellid brachiopod shells has been discussed for decades and continues to attract attention. This noteworthy modification of the anterior margin morphology during the ontogeny has evolved several times in rhynchonellids, and seems to reflect a genetic basis. First, we try to clarify the terminology regarding asymmetrical, dissymmetrical and symmetrical shells that has existed since the beginning of the 20th century. The Cretaceous populations observed clearly exhibit antisymmetry (also called random asymmetry). During the Cretaceous, some populations of Cyclothyris McKoy, 1844 include a mixture of truly asymmetrical specimens and others that exhibit an intermediate degree of asymmetry, herein called atypical morphologies. Shapes of specimens coming from two different locations in France were captured using geometric morphometrics. We used the range of different morphologies: 1) to test alternative hypotheses about the ontogeny of asymmetry; 2) to test for the possibility of several morphogroups; and 3) to discuss the determinism of the asymmetry.

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Could the asymmetrical commissure in rhynchonellide brachiopods be an adaptive trait?

Cited by 2 publications

References 26 publications

A new asymmetric rhynchonellide from the Cretaceous of the Eastern Prebetic (Southeastern Spain)

A new asymmetric rhynchonellide from the Cretaceous of the Eastern Prebetic (Southeastern Spain)

Shell asymmetry in Cretaceous Cyclothyrididae (Brachiopoda): variability, ontogeny and terminology

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