The Las Hoyas fossil site consists of laminated mudstones (lithographical limestones) that result from a shallow-lake sedimentation during the Upper Barremian (Lower Cretaceous). These mudstones contain a large quantity of fossil specimens with an exceptionally good preservation of soft parts, which includes Las Hoyas as one of the most famous Konservat-Lagerstätten [13].

Geologically, the Las Hoyas outcrop is located in the Las Hoyas syncline (Serranía de Cuenca, Iberian Ranges). The continental rocks from the Las Hoyas syncline were deposited in a little sedimentary basin, named Cubeta de Las Hoyas, which was integrated into a bigger one, named Iberian Basin [4]. The Cubeta de Las Hoyas was one subsident block with active sedimentation from the Iberian Basin, compartmented as a result of distensive tectonic phase of an intracontinental rifting, during the Lower Cretaceous. All the sediments deposited in the Cubeta de Las Hoyas are included in the La Huérguina Fm., Hauterivian–Barremian in age. The biostratigraphic studies with palynomorphs (pollen and spores), charophytes, and ostracods suggest that the age of the Las Hoyas fossil site is Upper Barremian (115 Myr BP) [2].

Order Coleoptera Linné, 1758

Suborder Polyphaga Emery, 1886

Superfamily Cucujoidea Latreille, 1802

Family Parandrexidae Kirejtshuk, 1994

Type genus. Parandrexis Martynov, 1926

Addition to description. Body elongated and subflattened, with thin and apparently evenly scattered punctation. Head large and transverse, with large- to medium-sized eyes; quite long 11-segmented subfiliform antennae attached between mandibles and eyes; long and narrow mandibles; long segments of maxillary and labial palpi; wide mentum whose sides almost reach edges of eyes. Prothorax widened anteriorly (thus evidently increasing mobility of the block combined head and prothorax). Coxae narrowly separated. Procoxae transverse, with trochantin exposed and looking like narrowly closed posteriorly; all coxae flat. Prosternal process more or less projecting beyond the level of posterior margin of procoxal cavities. Mesocoxal cavities transversely oval. Metathorax comparatively long, and with submesocoxal lines, but without traces of parametacoxal and medial sutures. Metacoxae subrectilinearly transverse and nearly reaching lateral edge of body. Abdomen including five ventrites, apparently not fused and of approximately equal length. Elytra complete or slightly shortened, with well-developed epipleura, forming distinct bend in plane of elytra. Prothorax, head and appendages of head (particularly antennae) with expressed sexual dimorphism. Legs moderately developed, with elongate trochanter, comparatively narrow femora and tibiae, apparently with 4-segmented tarsi and with ultimate tarsomere longest. Anal sclerite well developed and somewhat horseshoe-shaped.

Remarks. The family Parandrexidae should be regarded as a member of the superfamily Cucujoidea as was grounded by Kirejtshuk [7] and [8]. The strongly transverse flattened procoxae with exposed trochantin are characteristic for this family and few other Cucujoid families, such as Nitidulidae, Kateretidae, Smicripidae, Boganiidae, and Byturidae. Other characters of thorax also support the ascription of this family to the Cucujoidea. The general appearance of members of Parandrexidae has some characters similar to those of anthophilous groups of these families (particularly to some Paracucujinae from the Boganiidae as well as some Epuraeinae, Meligethinae, and Mystropinae from the Nitidulidae), including in transformation of antennae, mandibles and palpi of large, elongate and prognathous head, movable articulation between prothorax with head, on the one hand, and the rest more or less consolidated part of body, on the other one. Besides, the outline of leg segment, elongate trochanter, male anal sclerite and type of sexual dimorphism are similar to those among Cucujoidea rather than to any other superfamilies. It is possible to preliminarily admit that the Parandrexidae represents one of first offspring from ancestors of the Cucujoidea in general, and it seemed to have some phyletic connections with Nitidulidae, unless a further deeper cladistic analysis of cucujoids is needed to clarify the relationships between the different families among Cucujoidea.

Since its description, the genus Parandrexis has been considered as a member of the Cerambycidae and Boganiidae [1] and [10]; in 1994, Kirejtshuk considered that the genus should be placed in a new separately family [7]. Unfortunately, the systematic position of this new family within Cucujoidea remains uncertain, due to the lack of sufficient characters in remains available for study.

The genus Parandrexis is characterized by the antennae with length longer than the head, and also the head at least twice longer than the pronotum. The pronotum of the Parandrexis species is strongly widened anteriorly and with posterior angles obtuse and indistinct; their prosternal process is narrower than femora, slightly widened or not widened at apex and scarcely extended posteriorly from procoxae 5.5–18.0 mm. In 1983 Hong published a new species of Parandrexidae that he named ‘Parandrexia beipiaoensis g.s.n.’ [6]. However, this species has a habitus quite characteristic of the other species of the genus Parandrexis, but differing from others known from Karatau in its much larger and somewhat more slender body. The figure of the holotype published in Hong's original description shows the male anal sclerite very similar to that in many nitidulid groups, as well as the trace of submesocoxal lines and elongated trochanter supporting the opinion on placement of this family among the superfamily Cucujoidea.

Because of the structure of the adult mouthparts (elongated mandibles and long maxillary and labial palpi), the comparatively large eyes and prognathous head, Kirejtshuk proposed an open mode of life for the members of this extinct family, which could have lived on the surface of the strobiles of Mesozoic gymnosperms [7]. The Las Hoyas fossil site contains many remnants of conifers such as Araucariaceans and Cheirolepidaceans, which, as was supposed before for members of this family from Karatau, could have been host plants for specialized species of the family Parandrexidae.

According to the actual palaeogeographical maps [17], the three fossil sites where members of Parandrexidae family have been found (Jinlongshan, Karatau and Las Hoyas) were located in the subtropical-tropical areas, with cool or warm temperate floras.

Genus Martynopsis gen. n.

Type and only species. Martynopsis laticollis sp. n.

Etymology. The name of the new species is devoted to the Russian palaeoentomologist, A.V. Martynov, who proposed the name for the type genus of the family, and ‘opsis’ (= appearance).

Diagnosis. The type species of this new genus from the Lower Cretaceous of Spain shows similarities in the body outline and other characters to the species of Parandrexis. Martynopsis gen. n. differs from Parandrexis species in the antennae subequal in length to head (taken without mandibles), each of these organs sub-equal in length to the pronotum; pronotum subtrapezoidal, with the anterior and posterior edges comparable in width and with the posterior angles more distinct; prosternal process about as wide as femora, very widened at apex and somewhat extended posteriorly from procoxae. Length 13.4–15.0 mm, instead 11.0–18.0 mm in Parandrexis.

Martynopsis laticollis sp. n. (Fig. 1 and Fig. 2)

Material. Holotype LH-21091 part and counterpart, and paratype LH-24513, only the part, from personal collection of Armando Díaz-Romeral. All the material is housed in the Museo de las Ciencias de Castilla La Mancha, Cuenca, Spain.

Etymology. From the Latin words ‘latus’ (wide) and ‘collis’ (pronotum).

Stratum tipicum. Second lithosome of finely laminated limestones of La Huérguina Formation, Lower Cretaceous, Barremian [4].

Locus typicus. Las Hoyas fossil site, La Cierva, Serranía de Cuenca, Cuenca Province, Spain.

Diagnosis. As for genus.

Description. Length without mandibles 13.2 mm, length with mandibles 15.0 mm, body width 4.8 mm, antennae length 3.0 mm, elytra length 7.3 mm. Body elongate and subflattened. Head comparatively short, about as long as pronotum, widened behind eyes and with small notches at apex. Mandibles narrow and long, rather curved in distal fourth, slightly shorter than head. Antennae with 11 antennomeres and somewhat longer than head, without mandibles. Pronotum transverse, almost trapezoid, slightly widened anteriorly, anterior angles with a distinct top, anterior margin subtruncate; posterior angles obtuse, their top not distinctly visible. Prosternum apparently subflattened, with comparatively wide intercoxal process rather extended behind procoxae, strongly widened before apex that has widely rounded posterior edge, notosternal sutures distinct along entire length. Procoxae comparatively widely separated, transverse, apparently open posteriorly and with exposed trochantin. Mesosternum moderately short, medially with transverse isolated stripe at posterior edge. Mesocoxae moderately separated, moderately large and oval, closed externally. Metasternum moderately long; somewhat longer than prosternum with process, with well-expressed submesocoxal lines following along posterior edge of coxal cavities and deviating just at anterior angles of metasternum; parametacoxal lines (trace of transverse elevation at metacoxae) subparallel to anterior edges of metacoxal cavities, metepisternum moderately narrow, with shallow and indistinct punctures, about as large as half of last antennomere, interspaces between them more or less broader than punctures in diameter. Subsutural lines expressed along entire length and parallel; epipleura comparatively narrow, apparently distinctly folded laterally and do not reach apices. Legs moderately developed, with femoral apices somewhat exposed beyond lateral sides of body. Femora rather narrow, scarcely wider than prosternal process in the narrowest place, 4 to 5 times as wide as antennal flagella. Tibiae subequal in shape, slightly arcuate and with outer subapical angle somewhat projecting anteriorly, about twice narrower than femora. Exposed mesotarsus consisting at least of tarsomeres 1 to 3 moderately lobed. Elytra subparallel-sided and obliquely narrowed at apex, with most length at suture. Abdomen with visible segmentation dividing apparently ventrites (segment 1 longest), however elongate visible sutures, perhaps, belonging to borders between laterosternites and pleurites and between pleurites and tergites respectively.

Paratype . Beetle somewhat rotated in its position along body axis, quite tectonically deformed, especially in one side of pronotum. Total length somewhat shorter than holotype, but with subequal proportions of head, pronotum, and abdomen. Mandibles looking different (probably in sequence of general deformation). This specimen has traceable apices of one labial and one maxillary palps, which are as long as mandibles: last palpomeres of both palps rather long, narrow and subparallel-sided. Elytra seeming not so subparallel. Metatibia in contrast to that in holotype longest at inner edge.