Pipistrellus cinnamomeus Miller 1902 Referred to the Genus Myotis

In Short

This technical monograph resolves a long-standing taxonomic confusion regarding a small vespertilionid bat found in Mexico. By comparing original specimens and correcting historical naming errors, the authors determine that the species previously categorized as Pipistrellus cinnamomeus actually belongs to the genus Myotis. The text serves as an essential record of specimen analysis, demonstrating the meticulous work required to organize biological classification systems. It remains a foundational reference for mammalogists and those interested in the history of North American zoological research.

The Story

The narrative begins with a nomenclature puzzle dating back to 1902, when Gerrit S. Miller Jr. described a new bat, Pipistrellus cinnamomeus, based on a single specimen collected in Montecristo, Tabasco. Over the following decades, this name appeared in various regional lists, yet the animal’s true classification remained unsettled. The authors, E. Raymond Hall and Walter W. Dalquest, revisit this history with a collection of ten specimens gathered from five different Mexican localities. They aim to rectify the confusion caused by previous researchers who sometimes overlooked these specimens or mistakenly assigned them to other species.

The core of the investigation lies in a detailed comparison of anatomical features—specifically the teeth and the upper incisors—between the genera Pipistrellus and Myotis. The authors note that while Miller had initially distinguished the bat based on his understanding of tooth structure at the time, later developments in the study of bat anatomy made it clear that the creature possesses the diagnostic characteristics of Myotis. The complexity increases when the authors encounter Myotis lucifugus fortidens, a name applied by Miller and Allen in 1928 to a specimen that is, in fact, identical to the earlier Pipistrellus cinnamomeus.

Because cinnamomeus was already a preoccupied name within the Myotis genus due to a 1855 designation, the authors must navigate the strict rules of biological nomenclature. They conclude that the name Pipistrellus cinnamomeus is no longer available. Consequently, they reclassify the animal under the next valid name: Myotis fortidens.

The journey ends with a formal diagnosis of Myotis fortidens, commonly known as the Cinnamon Myotis. The authors provide comprehensive physical measurements and detailed physical descriptions, distinguishing this species from its relatives through its specific cranial structure and the absence of a third premolar. By reviewing the geographic ranges and comparing these ten specimens, they provide a definitive account that clarifies the bat’s identity and its place within the broader spectrum of American Myotis species. The conclusion is not just a name change, but a clarified understanding of how this bat fits into the evolutionary landscape of the Isthmus of Tehuantepec and the surrounding Mexican coasts.

How It Unfolds

The historical context The authors introduce the original 1902 description of Pipistrellus cinnamomeus and acknowledge its subsequent appearances in scientific records. They immediately establish that the initial classification was based on a very limited sample size, setting the stage for their own broader examination.

The diagnostic analysis The narrative shifts to a rigorous technical comparison of the genera Pipistrellus and Myotis. By focusing on the shape of the upper incisors and the number of premolars, the authors provide the anatomical evidence required to justify the shift in the bat's genus.

The correction of errors The authors trace the 1928 introduction of Myotis lucifugus fortidens, demonstrating through geographic and morphological evidence that it is a synonym for the earlier species. They explain the necessity of discarding the older, preoccupied name in favor of the newer, valid one to comply with taxonomic standards.

The final classification The report concludes with a formal, detailed definition of Myotis fortidens. By presenting extensive tables of cranial and external measurements, the authors offer a final, empirical summary that serves as the definitive reference for the species' physical characteristics.

The People

The figures in this account are the zoologists whose work shaped our understanding of this species. Gerrit S. Miller Jr. stands as the central initiator; he is the original observer who named the bat in 1902. His later work with G. M. Allen in 1928 unintentionally created the taxonomic confusion the authors must solve, as they assigned a new name to a species already described.

E. Raymond Hall and Walter W. Dalquest act as the modern auditors of this history. Their goal is precision; they are driven by the need to synthesize scattered data and apply modern standards to older, incomplete findings. They do not merely critique their predecessors but systematically review the physical "holotypes"—the original specimens—to reach their conclusions. Walter W. Dalquest, in particular, contributes significantly through his fieldwork, as he collected several of the crucial specimens in Veracruz that allowed the team to see a fuller picture than Miller had in 1902. Through their collaboration, they move from uncertainty to a settled, consensus-based taxonomy, resolving the conflicting identities of the Cinnamon Myotis.

In Its Own Voice

Regarding the physical appearance of the specimen, the authors note:

"Superficially it has much the appearance of an unusually red Myotis lucifugus, and only on examination of the teeth do the animal's true relationships become apparent."

In discussing the anatomical distinction between the two genera, the authors observe:

"In Myotis the outer upper incisor is distinctly larger than the inner, whereas the two incisors are of approximately equal size in Pipistrellus."

Reflecting on the need for further global research, the authors suggest:

"It may reasonably be asked if Myotis and Pipistrellus should be retained as separate genera if the only constant difference between the two is subequal versus unequal upper incisors."

What It's Really About

At its heart, this book is an exercise in the rigorous order of scientific classification. It explores the tension between historical observation and evolving knowledge, illustrating how science self-corrects over time. The fundamental question is one of biological identity: how do we define a species when the physical evidence is subtle and easily misinterpreted? The authors grapple with the importance of the "type specimen," emphasizing that truth in biology relies on the physical reality of the creature rather than just the names assigned to it in literature. It is an argument for the necessity of revisiting past conclusions with new specimens and a clearer diagnostic lens, reminding us that knowledge is a cumulative process that demands constant verification.

Why Read It Today

This text is designed for the reader who values the "detective work" of natural history. It will appeal to those who enjoy seeing the methodical, evidence-based process by which scientists refine our map of the living world. The prose is clean, technical, and entirely devoid of unnecessary flourish, making it a refreshing, grounded read for those interested in the mechanics of taxonomy.

Readers should be prepared for a highly specialized experience. The book functions as a scientific report, meaning it is dense with measurements, geographic data, and Latin terminology. There is no narrative fluff; it is a document of record. While the language is accessible, the subject matter is narrow, assuming the reader has some patience for lists and anatomical descriptions. What stays with you is a sense of respect for the sheer amount of archival work required to fix a single error in the biological record. For a student of biology or a curious enthusiast of the history of science, this work stands as a clear example of the scholarly pursuit of accuracy. It serves as a reminder that every animal name we see in a textbook is the result of such patient, deliberate, and often complex debate.