Characterization of coelacanth scales from the Early Cretaceous freshwater locality of Las Hoyas, upper Barremian (Cuenca, Spain)

Abstract

Coelacanths are rare, mostly marine fi shes, but the species from the Lower Cretaceous Spanish locality of Las Hoyas (Barremian) is a freshwater form and we know almost nothing about it. The Las Hoyas specimens are very rare and relatively incomplete, but there are still many things we can learn from the isolated skeletons and scales. First, the coelacanth scales were distinguished from other superfi cially similar scales (i.e., other "amioid" scales). Coelacanth scales are distinguished by the presence of a smooth central surface, a particular pattern of arrangement of concentric growth cessation marks, and mainly a relatively short posterior fi eld with thick elongated ridges. Only a few articulated coelacanth specimens have been recovered from Las Hoyas to date, and only 7.3% (n = 11) of the total isolated scales are coelacanth. The Las Hoyas coelacanth scales represent relatively large individuals. This suggests that a natural population of the coelacanth may have not inhabited permanently the freshwater pool represented RESUMEN

Heteropelta boboi n. gen., n. sp. an armored archosauriform (Reptilia: Archosauromorpha) from the Middle Triassic of Italy

“…However, they do not show the growth lines that are typical of fish scales. Furthermore, the only fish remains found associated with the reptile bones from the TAF are two skull bones of a large coelacanthiform and the osteoderms with fingerprint-like ornamentation do not resemble the scales of the coelacanthiforms ( Martín-Abad et al, 2017 ).…”

The ecology of the Lower Cretaceous coelacanths from Las Hoyas Konservat- Lagerstätte (Cuenca, Spain): A new insight after the integration of palaeontological and sedimentological data

“…4). A preliminary observation of the articulated material (Poyato-Ariza & Wenz, 1995; Poyato-Ariza & Martín-Abad, 2016a) as well as the detailed anatomical study of the scales (Martín-Abad et al, 2017b) does not show differences that could suggest the presence of more than one species. Las Hoyas' fossil collection is housed at Museo de Paleontología de Castilla-La Mancha in Cuenca (MUPA).…”

“…MUPA-LH LH 415, 840a/b, 930, 2328, 2916a/b, 5089a/b, 5276a/b, 9406a/b, 13679, 17011, 28210a/b, 37156, 37179. The Las Hoyas coelacanth scales are of the amioid type, but the isolated scales can reliably be distinguished from other amioid scales present at the locality (i.e., scales of the three amiiform fishes; Martín-Abad, 2016) by the presence of a smooth central surface, a particular pattern of arrangement of putative concentric growth cessation marks, and mainly a relatively short posterior field with thick elongated ridges (Martín-Abad et al, 2017b).…”

“…Habitat partitioning is common in recent wetlands, where the mosaic of blurred ecotones generates a variety of microhabitats (van der Valk, 2006;van der Valk & Warner, 2009), including both deeper and shallower, more calm waters. A similar study was carried out focusing on the coelacanth remains at Las Hoyas (Martín-Abad et al, 2017b), even though coelacanths are very rare at this site. This study shows that most of the coelacanth remains would represent relatively large-sized individuals, thus suggesting that a natural population may have not inhabited permanently the part of the wetland recorded at the excavated area of Las Hoyas, because small individuals should be the most common sizes.…”

“…Altogether, these data led to four non-mutually exclusive hypotheses to explain their population dynamics: 1) the coelacanth population was much smaller than that of other fishes at the locality; 2) this species only inhabited Las Hoyas for a (geologically) short period (i.e., coelacanth remains would only be recorded in some particular layers); 3) the coelacanth did not live at all at the excavated area of Las Hoyas, but in a different part of the wetland, and the remains would have been transported into the locality; 4) the coelacanth practiced habitat partitioning. The objective of the present study is to further explore the hypotheses proposed by Martín-Abad et al (2017b) by analyzing and interpreting the sedimentological characteristics of the fossiliferous layers where the coelacanth remains have been preserved, in terms of environments and environmental evolution.…”