Data from: Quantifying the completeness of the bat fossil record

Bats (Chiroptera) are one of the most successful extant mammalian orders,
uniquely capable of powered flight and laryngeal echolocation. The timing
and evidence for evolution of their novel adaptations has been difficult
to ascertain from the fossil record due to chronological gaps (e.g. during
the Palaeocene) and the fragmentary nature of most fossil bat material.
Changes in fossil specimen completeness through time and space can bias
our understanding of macroevolutionary processes. Here, we quantify the
quality of the bat fossil record using skeletal and character completeness
metrics, which respectively document what proportion of a complete
skeleton is preserved for a specimen, and the proportion of phylogenetic
characters that can be scored for a specimen. Completeness scores were
collected from the literature for 441 valid fossil bat species in 167
genera from the Eocene to Pleistocene. All metrics record similar temporal
patterns: peak completeness in the Lutetian Stage reflects the presence of
Lagerstätten, while subsequent stages have very low completeness with the
exception of an Aquitanian high and a Pleistocene peak in skeletal
completeness. Bat completeness is not correlated with intensity of
sampling through geological time but has a weak negative correlation with
publication date. There is no correlation between taxonomic richness and
completeness, as the bat fossil record predominately consists of
diagnostic but isolated teeth. Consequently, bat skeletal completeness is
the lowest of any previously assessed tetrapod group, but character
completeness is similar to parareptiles and birds. Bats have significantly
higher character completeness in the northern hemisphere, likely due to
heightened historical interest and presence of Lagerstätten. Taxa derived
from caves, fissure fills and sink holes are more complete than those from
fluviolacustrine and marine deposits, but do not preserve highly complete
specimens.

翼手目（Chiroptera）蝙蝠是现存最成功的哺乳动物目级类群之一，唯一具备动力飞行与喉回声定位能力。由于化石记录存在年代空白（如古新世时期）且多数蝙蝠化石材料保存破碎，学界长期难以从化石记录中厘清其创新性适应性状的演化时序与相关证据。化石标本的完整性随时间与空间发生的变化，可能会偏倚我们对大进化（macroevolutionary）过程的认知。本研究通过骨骼完整性与性状完整性两项量化指标，对蝙蝠化石记录的保存质量进行评估：前者用以衡量标本中完整骨骼的留存比例，后者则统计可用于该标本的系统发育性状得分占比。研究团队从已发表文献中采集了始新世至更新世时期，隶属于167个属的441个有效蝙蝠化石物种的完整性数据。各项指标均呈现相似的时间分布模式：吕特蒂亚期的完整性峰值，对应该时期存在优质化石埋藏库（Lagerstätten）；后续多数地层单元的完整性水平极低，仅阿基坦阶存在一次完整性高峰，且更新世时期的骨骼完整性出现显著峰值。蝙蝠化石的完整性与地质时间尺度上的采样强度并无关联，但与研究成果的发表年份呈微弱负相关。分类类群丰富度与完整性之间不存在相关性，这是因为蝙蝠化石记录主要由具有分类诊断价值但孤立的牙齿化石构成。因此，蝙蝠的骨骼完整性是所有已评估四足动物类群中最低的，但其性状完整性与副爬行动物、鸟类相近。北半球的蝙蝠化石性状完整性显著更高，这可能源于学界对该区域更高的历史研究关注度，以及当地存在更多优质化石埋藏库。采自洞穴、裂隙充填与落水洞沉积中的蝙蝠类群，其标本完整性高于河湖相及海相沉积中的类群，但前者并未产出高度完整的蝙蝠化石标本。