A new family, genus and species of Tanaidacea (Crustacea; Apseudomorpha) from the Lower Cretaceous (Aptian) of Chiapas, Mexico: Systematic revisions , including designation of two new Paleozoic families, and paleoenvironmental observations
Por:
Heard, Richard W., Morales-Nunez, Andres G., de Lourdes Serrano-Sanchez, Maria, Coutino, Marco A., BARRAGAN, RICARDO, Vega, Francisco J.
Publicada:
1 oct 2020
Resumen:
A new fossil apseudomorphan tanaidacean, Protoapseudoides espinalensis
gen. et n. sp., from the Chiapas Region of Mexico, is described and
placed within the new monotypic family Protoapseudoidae. Its description
is based on more than 1000 specimens collected from the Lower Cretaceous
(Aptian) in laminar dolomites from the El Espinal quarries (Sierra Madre
Formation). The presence of a telsonic somite partially fussed, but
ventrally distinct indicates that the body form of this new tanaidacean
may represent a transitional evolutionary step between fossil
Anthracocaridomorpha and the extant Apseudomorpha. The presence of an
apparently fused, but a ventrally delineated telsonic somite indicates
that the new family may represent a transition of an
anthracocaridomorphan to an apseudomorphan body form. A new family, the
Protoapseudoidae, is designated to accommodate the unique combination of
morphological features exhibited by the new Chiapas species. These
features include the presence of a vestigial telson, a blunt
subtriangular rostrum, vestigial anterolateral processes on the
carapace, and a single male genital cone, coupled with the absence of
eye stalks, coxal spine on the first pereopod, and spines or lateral
processes on carapace and pereon. This combination of characters
distinguishes the new family from all the other known extinct and extant
families within the Order Tanaidacea. Though clearly indicated
ventrally, unlike the Anthracocaridomorphan, the vestigial telsonic
somite of new Chiapas family appears not to be ``independent'' or
``articulated,'' and is functionally fused with pleonite-6 to form a
pleotelson. Accordingly, the new family is tentatively placed within the
suborder Apseudomorpha. The Protoapseudoidae appears, at least
superficially, to have possible affinities with both the Paleozoic genus
Ophthalmapseudes and to the members of the extant parapseudid
Discapseudes-Halmyrapseudes Complex. The Paleozoic monotypic,
anthracocaridid genera Eucryptocaris and Ophthalmapseudes, due to their
unique morphological features and temporal distances, are hierarchized
to family rank. As Eucryptocaridae n. fam. and Ophthalmapseudidae n.
fam. Due to their based similarity, the superfamily Jurapseudoidea, is
considered a junior synonym of the superfamily Apseudoidea. The possible
relationship between the extinction of Protoapseudoidae and the
emergence of parapseudid tanaidaceans in Americas is discussed. The
morphological changes recorded between the Cretaceous fossil
tanaidaceans, including the review of those 25 species as far known, and
their extant relatives are considered to propose the timelines on the
evolution of different tanaidacean morphotypes. Also, here are discussed
the taphonomic and paleoenvironmental Condition that allow the fossil
preservation of tanaidaceans.
Filiaciones:
Heard, Richard W.:
Univ Southern Mississippi, Dept Coastal Sci, Gulf Coast Barraga Manzo Res Lab Campus, Ocean Springs, MS 39564 USA
Morales-Nunez, Andres G.:
Univ Maryland Eastern Shore, NSF CREST Ctr Integrated Study Coastal Ecosyst Pr, Dept Nat Sci, Princess Anne, MD 21853 USA
de Lourdes Serrano-Sanchez, Maria:
Univ Nacl Autonoma Mexico, Fac Ciencias, Ciudad Univ, Coyoacan 04510, Cdmx, Mexico
Coutino, Marco A.:
Museo Paleontol Eliseo Palacios Aguilera, Secretaria Medio Ambiente & Hist Nat, Calzada Los Hombres Ilustres S-N, Tuxtla Gutierrez 29000, Chiapas, Mexico
BARRAGAN, RICARDO:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Coyoacan 04510, Cdmx, Mexico
Vega, Francisco J.:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Coyoacan 04510, Cdmx, Mexico
|