Portugalophis

Portugalophis lignites is a Late Jurassic squamate described from three jaw fossils recovered from the Guimarota coal mine in Portugal. Its long upper jaw, tooth arrangement and other details led its authors to identify it as one of the earliest known snakes. The holotype is only a left maxilla; the other known pieces are a lower jaw and a partial second maxilla. There is no complete skull, spine or associated skeleton. Its snake affinity is supported by a combination of jaw characters, but its exact position near the base of the snake tree remains uncertain. Portugalophis is included in the ancient lizard and snake catalogue.

Quick facts

A name tied to a coal mine

Michael Caldwell, Randall Nydam, Alessandro Palci and Sebastián Apesteguía named Portugalophis lignites in 2015 while reassessing early snake fossils. The generic name combines Portugal with the Greek word for snake. The species name refers to lignite and the coal-bearing rocks of the Guimarota mine, where the material was collected. The type locality lies near Leiria in western Portugal.

The holotype is MG-LNEG 28091, a left maxilla held by the Geological Museum in Lisbon. The referred material comprises MG-LNEG 28094, a left dentary, and MG-LNEG 28100, a partial left maxilla. These are three separate pieces, not parts of one individual shown in articulation. Their shared diagnostic features support the named species, but the sample gives no direct view of the back of the skull or the rest of the skeleton.

Guimarota is known for fossil-bearing coal deposits formed in a coastal lowland setting. Fine-grained sediments and mine workings yielded remains of small vertebrates that would be difficult to find in more exposed deposits. The local environment provides geological context; it does not show that this animal lived inside a mine-like habitat or that each jaw bone was buried exactly where the animal died.

What the jaws preserve

The holotype maxilla is a narrow, tooth-bearing bone from the left side of the upper jaw. It carries 15 alveoli, with preserved teeth in some positions. The tooth crowns curve backwards and have cutting edges. A second, partial maxilla provides a comparison but does not fill the missing rear skull. The known lower jaw likewise preserves a limited section rather than a whole mandible.

The dentary has 15 tooth positions, six of which retain teeth in the described specimen. The alveoli and the way the teeth attach are among the characters used to compare Portugalophis with other early squamates. Some details resemble those of early snakes, while individual traits also occur in lizards. No single tooth feature, considered alone, demonstrates that the animal belongs inside the crown group of living snakes.

The fossils do not include vertebrae, ribs, limb bones or a skull roof. They therefore give no measured body length, tail proportions or direct evidence for the characteristic elongate body of later snakes. A long-bodied reconstruction may be plausible from its proposed affinities, but it would extrapolate well beyond the material assigned to Portugalophis itself.

An early snake, with a qualified placement

The 2015 study placed Portugalophis among early snake-line fossils from the Middle Jurassic to Early Cretaceous. Its age makes it an important data point in discussions of when snakes originated and how early members of the group were distributed. The assignment was based on a phylogenetic analysis of anatomical characters, not on a complete skeleton or a preserved behavioural trait.

Later work has highlighted how difficult it can be to distinguish the earliest snakes from other early squamates when fossils consist of isolated jaws. Features once treated as uniquely snake-like may also occur in other lineages, and missing parts cannot be coded in a character matrix. The result is a plausible snake affinity alongside uncertainty about exactly which branch Portugalophis occupies.

It is useful to compare Portugalophis with Parviraptor, another early squamate historically discussed in relation to snakes, and with the much younger snake Dinilysia. These comparisons frame evolutionary questions; they do not establish a direct ancestor-descendant sequence. Each fossil represents a side branch unless evidence demonstrates otherwise.

What its setting and anatomy can tell us

The Guimarota coal beds formed during the Kimmeridgian, about 155 million years ago. Their assemblage records a diverse Late Jurassic ecosystem, but the isolated jaws do not reveal whether Portugalophis hunted on land, along water margins or in another microhabitat. The location and age are secure at a broad geological scale; the animal’s daily range is not directly preserved.

Backward-curving teeth with cutting edges would have helped grip or cut food. That is a functional interpretation consistent with a small predatory squamate. No stomach contents, bite marks linked to the species or coprolites have been found with the known material, so naming a particular prey group would go beyond the evidence.

The secure portrait is deliberately modest: a small Jurassic squamate represented by several diagnostic jaw bones, with an early snake placement supported by comparative anatomy. Its skin, colour, eye, tongue, locomotion and total size remain unknown. A future discovery of associated skull and vertebral material could test whether the proposed snake-like features belong to a broader anatomy or were concentrated in the jaws.