Comment on: Álvaro, J. J., Esteve, J. & Zamora, S. 2019. Morphological assessment of the earliest paradoxidid trilobites (Cambrian Series 3) from Morocco and Spain [Geological Magazine]

Abstract

AbstractÁlvaro et al. (2018) argued that at least six species of Acadoparadoxides described from the lower–middle Cambrian boundary interval successions in the Anti-Atlas of Morocco all belong to Acadoparadoxides mureroensis (Sdzuy, 1958), which was first described from the Iberian Chains, Spain. Their study is based entirely on a morphometric analysis, which ignores the stratigraphic occurrences of particular morphotypes, deformation-related compaction of individual sclerites and their original relief, and thus underestimates some of the earlier described differences between these species. Their synonymization of a number of named Acadoparadoxides species is based on the morphometric approach that they rely on to distinguish between a number of congeneric species. A morphometric approach as applied by Álvaro et al. will lead to an apparent synonymy based on sclerites of similar taxa. Thus, morphometric study must be complemented by an analysis of which morphologically distinctive sclerites (i.e. cranidia and pygidia) are stratigraphically associated, and evaluation of which measurements are more critical to distinguishing sclerites that may represent distinct taxa, and the recognition of related character sets. Apart from demonstrating problems in the conclusion of Álvaro et al., our more inclusive approach of morphologic and stratigraphic analysis works to reassert the diagnostic characters and differences between six earlier named species of Acadoparadoxides. Our conclusions also emphasize the taxonomic problems associated with the identification and morphological variation of A. mureroensis owing to tectonic deformation of its topotype material and to questionable taxonomic assignment of Acadoparadoxides specimens from the Iberian sections.

Reply to Comment on: Álvaro J.J., Esteve, J. & Zamora, S. 2019. Morphological assessment of the earliest paradoxidid trilobites (Cambrian Series 3) from Morocco and Spain [Geological Magazine] by Geyer G, Nowicki J, Żylińska A & Landing E

“…According to their results, some species previously proposed by Geyer & Vincent (2015) cannot be separated biometrically into distinct morphotypes, and we 'suggested their synonymy until 3D statistical analyses are available based on material preserved in carbonate and silica nodules' (sentence taken from Abstract and Conclusions). Geyer et al's (2019) contribution sets out to contradict Álvaro et al's (2018) bivariate and Principal Components Analyses (PCA) but offers only qualitative descriptions of morphological outlines and bivariate relationships that are not justified by their own illustrated specimens. Their criticism is based on the assumption that biometric results cannot improve qualitative descriptions of what they call 'mosaics of characters'.…”

“…As a result, Geyer et al's (2019) paper is not only a 'Comment on Álvaro et al (2018)', but also an 'Erratum for Geyer & Vincent (2015)'. Geyer et al (2019) criticize some statements that do not occur in Álvaro et al (2018). They state that when reading that 'several species recently erected in Morocco are suggested as synonyms of A. mureroensis until 3D statistical analyses are available on material preserved on carbonate or silica nodules', the reader will understand that 'Álvaro et al (2018) argued that at least six [sic] species of Acadoparadoxides belong to A. mureroensis'.…”

“…In the following, we will highlight how some of Geyer et al's comments are flawed by misconceptions, misinterpretations, use of questionable methods and misuse of personal communications. After comparing the works of Geyer & Vincent (2015) and Geyer et al (2019), it is clear that the authors have modified the taxonomic diagnoses of what are still 'overlapping characters'. As a result, Geyer et al's (2019) paper is not only a 'Comment on Álvaro et al (2018)', but also an 'Erratum for Geyer & Vincent (2015)'.…”

“…After comparing the works of Geyer & Vincent (2015) and Geyer et al (2019), it is clear that the authors have modified the taxonomic diagnoses of what are still 'overlapping characters'. As a result, Geyer et al's (2019) paper is not only a 'Comment on Álvaro et al (2018)', but also an 'Erratum for Geyer & Vincent (2015)'. Geyer et al (2019) criticize some statements that do not occur in Álvaro et al (2018).…”

Unexpectedly curved spines in a Cambrian trilobite: considerations on the spinosity in Kingaspidoides spinirecurvatus sp. nov. from the Anti-Atlas, Morocco, and related Cambrian ellipsocephaloids

“…However, these quarries are established in the lower and middle part of the Bréche à Micmacca Member, which belongs to the Morocconus notabilis Biozone. This part of the succession is rich in large specimens of Acadoparadoxides species (such as A. briareus and A. levisettii) as well as species of Hamatolenus (such as H. vincenti and H. marocanus) (Geyer 1993;Geyer and Vincent 2015;Geyer et al 2019), which are frequent objects on the fossil market. The fossils from these strata are characterized by the ochre or red-brown colour of the objects on a yellow sandstone matrix due to the shell substance being largely leached.…”