Tijubina

Tijubina pontei is a small lizard from the Late Aptian Crato Formation of northeastern Brazil. Its only known fossil, MPSC-V 010, is an articulated juvenile skeleton that preserves parts of the skull, limbs and body, together with impressions of scales. A 2012 redescription confirmed that the animal belongs among squamates and compared its anatomy with other fossil lizards. The fossil is unusually informative for a Gondwanan Cretaceous lizard, but its immaturity and incomplete skeleton leave adult proportions and exact relationships unresolved. Tijubina appears in the ancient lizard and snake catalogue.

Quick facts

One specimen, two stages of study

Francisco Bonfim-Júnior and Ricardo Marques named Tijubina pontei in 1997 from a fossil found near Nova Olinda in Ceará State. Tiago Simões redescribed the holotype in 2012 after noting that the original account did not document many diagnostic details or clearly separate Tijubina from other Crato lizards. The redescription treated MPSC-V 010, housed at the Museu de Paleontologia de Santana do Cariri, as the only specimen then securely assigned to the species.

The fossil is preserved on a thin limestone slab in dorsal view. Parts of the skull are fragmentary, while the trunk, shoulder region, forelimbs, portions of the pelvis and hindlimb impressions retain useful anatomical information. The fossil measures about 46.6 millimetres from the snout to the pelvis, a measurement of the preserved individual rather than a full body length. It should not be presented as an adult maximum: the bones show that this animal had not completed skeletal growth.

The Crato Formation records a lake system in the Araripe Basin. Laminated limestones preserve fishes, plants, insects and other vertebrates, including lizards. That setting explains the exceptional preservation potential, but a skeleton found in lake sediment does not establish that the animal lived in water. Its remains may have reached the lake after death from surrounding land. The fossils define a geological context, not a precise daily habitat.

The scales are impressions, not colour

The slab preserves scale impressions along the neck, trunk and tail. The redescription distinguished very small rhomboid scales on the neck from larger rhomboid elements on the underside of the trunk. Along the ventral tail, the scales form transverse annuli. These outlines are direct evidence of scale arrangement in the preserved regions and make Tijubina more informative than a fossil represented only by bones.

An impression records boundaries and shape, not pigmentation. No preserved colour pattern or chemical evidence establishes whether the living lizard was bright, dark, striped or plain. A naturalistic drawing therefore has to choose colours for visual clarity, while the fossil itself supports only the scale outlines and their relative sizes. The missing skin should not be filled with an elaborate pattern and described as known.

The trunk and tail impressions also do not amount to a complete skin cast. Some regions are faint or absent, and preservation varies across the slab. The safest reconstruction follows the parts that can be observed and labels any broader texture as an inference from other lizards rather than a feature seen on MPSC-V 010.

Anatomy behind the revised diagnosis

The 2012 study diagnosed Tijubina through a combination of features rather than one striking trait. The dentary lacks distinct posterodorsal and posteroventral processes. The posterior teeth have robust cylindrical bases and lack the cusps described in many other lizards. The tibia and fibula are close in length to the femur, and the feet are elongated. These details contribute to a character combination used in comparisons with other fossil lizards.

Those proportions have been used to discuss locomotion, but there is no trackway or observed motion. Elongated feet can contribute to functional interpretations, yet a juvenile skeleton may differ from adult proportions and the fossil is incomplete. Claims that Tijubina was definitively a fast runner, climber or shoreline specialist would go beyond the preserved evidence.

The original authors first compared the fossil with teiid lizards. Other researchers later proposed a rhynchocephalian identity, while subsequent studies returned it to Squamata. Simões considered it a basal scleroglossan outside Autarchoglossa, but explicitly noted that its systematic position required further clarification. That history is not a sequence of discoveries about a changing animal; it reflects how different character comparisons can alter a fossil’s placement.

What the juvenile fossil can establish

MPSC-V 010 preserves an immature lizard rather than an embryo or a newly hatched animal. Several skeletal features were still developing, so the proportions of the known specimen cannot simply be scaled up to produce an adult. The fossil gives a lower bound on body size for one individual, but it does not supply a reliable final length, mass or range of adult variation.

The specimen’s value is broader than its classification. It documents a relatively complete Early Cretaceous squamate from South America, a region with a sparse record of Mesozoic lizards. Comparisons with Dalinghosaurus help frame how preserved anatomy varies among Cretaceous lizards. Comparisons with Huehuecuetzpalli and Meyasaurus broaden the geographical picture, but do not imply direct ancestry.

What remains secure is a juvenile squamate from the Crato lake deposits, with an articulated partial skeleton and preserved scale impressions. It had elongated feet and a distinctive combination of jaw and tooth features. Its adult dimensions, original colour, exact ecology and closest relatives are still open questions. A second, better-preserved individual could test whether the diagnosis and proportions seen in the holotype represent the species throughout growth.