Hoyalacerta

Hoyalacerta sanzi was a very small lizard from the Early Cretaceous Las Hoyas site in Spain. Its holotype is a nearly complete skeleton preserved across a limestone slab and counter-slab. The fossil measures about 34 millimetres from snout to the base of the tail; the skull is approximately 10 millimetres long. A long trunk, 27 or 28 presacral vertebrae, short limbs and simple conical teeth can be studied directly. The exact branch where it belongs among early squamates is less settled. Compare it with other small fossil forms in the ancient lizard and snake catalogue.

Quick facts

A fossil split between slab and counter-slab

Susan Evans and Luis Barbadillo described Hoyalacerta sanzi in 1999. The name-bearing specimen is LH 11000a and b, the two surfaces formed when a fossil-bearing rock split. It is housed in the museum at Cuenca. Most of the small skeleton remains in anatomical order, although parts of the skull and left forelimb are displaced or incomplete. The femora and feet are not fully preserved.

Las Hoyas lies in Cuenca Province, in the Early Cretaceous La Huérguina Formation. The holotype comes from limestone unit III. The site is known for fine-grained deposits that preserve delicate small animals. Here, the rock surface records a skeleton rather than a complete three-dimensional body, so bone position and overlap affect some measurements.

The genus name refers to the Las Hoyas locality, and the species name honours Spanish palaeontologist José Luis Sanz. Before its formal description, the fossil had been grouped with small unidentified lizards from the site. A combination of measurable features allowed the authors to recognise a distinct form.

A compact body with short limbs

The snout-to-vent region measures about 34 millimetres, excluding the missing or incomplete tail beyond its base. The skull is roughly 10 millimetres long. The presacral vertebral series has 27 or 28 elements, depending on how one unclear vertebra is counted. That extended trunk is proportionally long for such a tiny lizard.

The forelimb was estimated at about 23.5 percent of snout-to-vent length and the hind limb at roughly 32.5 percent. The foot accounts for about a third of the hind-limb length. These measurements support the description of relatively short limbs, but the fossil does not show that the animal could not walk normally. Limbs that appear short can serve different functions depending on joint mobility, muscle and habitat.

The lower jaw carries around 40 closely spaced, simple conical teeth. They differ from the bicuspid teeth reported in other small lizards from Las Hoyas. Hoyalacerta has no heavy cranial ornament or obvious body armour. No stomach contents or associated prey identify what it ate; small arthropods are plausible for a lizard of this size, not a demonstrated menu.

What its family-tree position means

The original analysis placed Hoyalacerta outside the crown group of living lizards and snakes. Later studies have recovered varying positions, including near the stem of iguanians or elsewhere among early squamates. Large phylogenetic analyses compare suites of skull, jaw, vertebral and limb characters. When a fossil preserves only some features, changing the sampled taxa or interpretation of one bone can affect where it falls.

Being outside the crown group does not mean that Hoyalacerta was an unfinished or primitive animal in every respect. It had a distinctive body plan and had already lived after multiple branches of squamates evolved. A phylogenetic stem position describes its relationship to a later group, not its degree of success or completeness.

The skeleton is informative because its proportions are unusually measurable for a tiny Cretaceous lizard. Its branch on the tree is an inference that can be tested as new fossils and anatomical characters are added. The two statements are compatible: the body measurements are relatively secure, while the deeper relationship remains open.

Las Hoyas and the limits of reconstruction

The Las Hoyas limestone formed in a freshwater wetland system. Fine carbonate mud and quiet deposition helped preserve small vertebrates, including fish, amphibians, crocodile-line reptiles and turtles. Plants around the wetland included ferns and other Early Cretaceous vegetation. The locality gives Hoyalacerta a clear environmental setting, but it does not show where within that habitat the animal spent most of its time.

An elongated trunk and shorter limbs could have helped a small lizard move through dense ground cover or narrow spaces. That is a functional possibility, not a direct trace of behaviour. No burrow, trackway, prey remains or nesting material is associated with the holotype. Its original colour and detailed skin pattern are also unknown.

Some reconstructions show a particular posture or colour palette to make a tiny fossil legible to viewers. Those choices should not be confused with the measurements from LH 11000a/b. Hoyalacerta is best presented as a small, long-bodied Early Cretaceous lizard whose limbs and teeth are visible in one near-complete specimen, while its movement and precise phylogenetic position remain questions. Other early squamates in the catalogue offer comparisons without standing in for Hoyalacerta.