Laricola: a fossil seabird outside the modern gull family

Laricola is an extinct genus of charadriiform bird best known from Early Miocene deposits at Saint-Gérand-le-Puy in France. Nineteenth-century authors compared its bones with gulls, but a modern revision placed it outside the living gull family Laridae, among early members of the broader Laromorphae that includes gulls, terns and skimmers. Its scattered bones establish a flying bird with affinities to that group, while leaving details of its feeding and appearance uncertain. Read with other fossil seabirds in the extinct bird catalogue.

Quick facts

From Larus to Laricola

In the nineteenth century, Alphonse Milne-Edwards described several fossil birds from Saint-Gérand-le-Puy as species of Larus, the genus that includes living gulls. Later authors placed some of these remains in Laricola. As with many old fossil collections, the material was not a row of complete skeletons. It consisted of disarticulated bones gathered from deposits rich in remains of birds, mammals and other animals. That made it difficult to determine which bones belonged together and how many species were represented.

Vanesa De Pietri, Loïc Costeur, Marcel Guentert and Gerald Mayr re-examined the Lari material in 2011. They redescribed the earlier fossils, described Laricola intermedia and L. robusta, and separated additional material into the new genus Sternalara. Their revision also rejected some older assignments to Laricola. The outcome is a more carefully delimited genus than the one suggested by simply gathering all gull-like bones under a familiar living name.

A revised species list is not a claim that every bone at the locality has been conclusively matched to one species. Fragmentary samples can preserve overlapping and non-overlapping elements, and different individuals may be mixed in the same deposit. Taxonomy depends on diagnostic anatomy that can be compared, not merely on the fact that two bones came from the same fossil bed.

A stem member of Laromorphae

To test the genus’s relationships, the 2011 study analysed 41 skeletal characters across fossil and living charadriiform birds. The result placed Laricola outside crown-group Lariidae, the family containing modern gulls. It was instead among early representatives of Laromorphae, a larger branch that encompasses gulls, terns and skimmers. In evolutionary terms, it had affinities to the ancestry of those groups without being classified as a modern-type gull.

The distinction is based on a combination of structures in the skull and postcranial skeleton. The revision noted differences from gulls in the bill-bearing part of the skull, the arrangement of nasal openings, the mandible and several shoulder and wing features. Some humeral characters look relatively primitive, but the analysis does not rest on a single supposedly primitive bone. Relationships are inferred by comparing multiple characters together.

Phylogenetic placement is a scientific hypothesis tested against the material and character sample available. New fossils or alternative character codings can change a tree. Even so, the 2011 study directly challenges the casual use of “fossil gull” for every small charadriiform with a gull-like outline. A reconstruction may reasonably use a generalized laromorph form, but it should not present a modern gull species as the animal’s identity.

Species and the limits of fragmentary fossils

The revised genus includes L. elegans, the type species, along with L. totanoides, L. intermedia and L. robusta. The latter two were named in the 2011 revision. The epithets and diagnoses refer to differences among preserved bones and their proportions. They do not, by themselves, establish four separate plumage patterns or ecological roles.

Body size varied across the material assigned to the genus, from smaller to more robust forms. This variation must be interpreted with care because not every fossil element overlaps anatomically with every other one. A robust bone may be diagnostic, but it may also reflect the particular element, individual variation or the uncertain association of isolated specimens. The revision’s species diagnoses are based on comparisons of the available material rather than on complete series of skeletons.

Saint-Gérand-le-Puy is the central locality for the group, but the genus has also attracted discussion of other scattered fossils. Those outlying assignments require their own taxonomic checks. An age or geographic range should not be expanded simply because an isolated bone resembles the French specimens. Well-preserved evidence from one locality remains more secure than every historical attribution made elsewhere.

Likely habitat and what the bones cannot say

The Early Miocene deposits at Saint-Gérand-le-Puy formed around freshwater and brackish environments in a warm setting. The site preserves numerous birds associated with water. The general proportions of Laricola show that it retained functional wings and was capable of flight. Its leg bones are relatively slender, but the incomplete material does not provide a full reconstruction of its stance or gait.

Finding it among aquatic and shorebird fossils makes foraging around water plausible. A diet of small animals has also been proposed from the broad resemblance and habitat, but no stomach contents identify specific prey. The bill’s exact external shape, the timing of feeding, and whether individuals took food from mud, shallow water or the air are not directly recorded. Similarity to living gulls or terns helps generate comparisons; it does not turn those comparisons into observations of the fossil animal.

In contrast to highly specialized flightless seabirds such as the great auk, Laricola preserved a normal flying apparatus. Beyond that broad statement, flight speed, migration and daily range cannot be measured from the known bones. The evidence supports a flying member of the early laromorph radiation at a diverse water-associated locality, while leaving its exact niche open.