No abstract

El Soplao outcrop, an Early Cretaceous amber deposit recently discovered in northern Spain (Cantabria), has been shown to be the largest site of amber with arthropod inclusions that has been found in Spain so far. Relevant data provided herein for biogeochemistry of the amber, palynology, taphonomy and arthropod bioinclusions complement those previously published. This set of data suggests at least two botanical sources for the amber of El Soplao deposit. The ñrst (type A amber) strongly supports a source related to Cheirolepidiaceae, and the second (type B amber) shows non‐specific conifer biomarkers. Comparison of molecular composition of type A amber with Frenelopsis leaves (Cheirolepidiaceae) strongly suggests a biochemical affinity and a common botanical origin. A preliminary palynologlcal study indicates a regional high taxonomical diversity, mainly of pteridophyte spores and gymnosperm pollen grains. According to the preliminary palynologlcal data, the region was inhabited by conifer forests adapted to a dry season under a subtropical climate. The abundant charcoalified wood associated with the amber in the same beds is evidence of paleofires that most likely promoted both the resin production and an intensive erosion of the litter, and subsequent great accumulation of amber plus plant cuticles. In addition, for the first time in the fossil record, charcoalified plant fibers as bioinclusions in amber are reported. Other relevant taphonomic data are the exceptional presence of serpulids and bryozoans on the surfaces of some amber pieces indicating both a long exposure on marine or brackish‐water and a mixed assemblage of amber. Lastly, new findings of insect bioinclusions, some of them uncommon in the fossil record or showing remarkable adaptations, are reported. In conclusion, a documented scenario for the origin of the El Soplao amber outcrop is provided.

Significance We report on the unique discovery of Jurassic and Cretaceous carrion beetles (Silphidae) from China and Myanmar, early relatives of one of the most protected of beetle species in North America, and which clearly preserve evidence indicative of complex parental care. This finding represents the earliest evidence of parental care, a behavioral repertoire that is the first step in the development of truly social behavior and one that is intensely studied by ecologists, ethologists, and evolutionary biologists alike. Our fossils clearly span the origins of parent–offspring communication and allow us to provide a robust estimate of the time of origin for this complex behavior.