Concavenator: the humped hunter from Cuenca

Concavenator corcovatus is a medium-sized theropod known from an exceptionally informative skeleton discovered at Las Hoyas in central Spain. Its name refers to the “humped hunter from Cuenca”, a nod to the striking peak formed by two extremely tall neural spines over the hips. The bones document that unusual structure, but do not preserve a sail, hump of flesh or a definite function.

The holotype is unusually complete and articulated for a theropod, with impressions of scales around the foot and lower tail. Those impressions add rare evidence about parts of the skin, but they do not map the covering of the whole body. Interpretations of a row of bumps on the forearm as feather anchors are disputed. The animal's anatomy is therefore best understood by separating directly preserved details from plausible, unresolved reconstructions.

One near-complete skeleton establishes a Spanish Early Cretaceous theropod with a localised pair of very tall back spines and preserved scale impressions near the foot. It does not settle the soft-tissue shape of the hump, the presence of feathers over the body or the dinosaur's exact place on the theropod family tree.

Quick facts

Discovery at Las Hoyas

In 2003, a team led by Francisco Ortega returned to a fossil-bearing area at Las Hoyas and began excavating a large theropod skeleton from thin limestone. The bones lay in articulation and were distributed across several slabs. Preparing the specimen in the laboratory took more than two years. The holotype was catalogued as MCCM-LH 6666 and described in 2010 by Ortega, Fernando Escaso and José Luis Sanz. It is held at the Palaeontological Museum of Castilla-La Mancha in Cuenca.

The genus name combines a reference to Cuenca with the idea of a hunter; the species epithet corcovatus refers to a hump. The name captures the outline suggested by the vertebrae, but it should not be read as proof that the living animal carried a fleshy hump of a particular shape. Bone is directly preserved. Skin, muscle, fat and any ornamental covering are not.

Las Hoyas is known for finely layered carbonate deposits and fossils preserved in remarkable detail. The specimen's association makes it far more informative than an isolated tooth or a scattering of bones. Even so, one skeleton does not reveal the complete range of variation within a species, the anatomy of every age class or all of the soft tissues of the living animal.

Age and the Las Hoyas ecosystem

Concavenator lived during the Barremian stage of the Early Cretaceous, approximately 125 million years ago. Its type comes from the La Huérguina Formation in Cuenca province, Spain. Age assignments are based on geological correlations and the broader stratigraphy, rather than a precise date preserved in the bone. The Las Hoyas deposits record freshwater carbonate wetlands, ponds and associated habitats in a seasonal landscape.

Fossils from Las Hoyas include fishes, crustaceans, insects, amphibians, crocodylomorphs, lizards, birds and dinosaurs, alongside plants. That diversity describes a regional fossil assemblage, not necessarily one moment in which every named animal occupied the same pond. Layers accumulate over time, and carcasses can be transported or buried under different circumstances. The local deposits are valuable precisely because they preserve several lines of evidence, but each must be interpreted at its own stratigraphic and taphonomic scale.

Fine sediment and microbial mats helped preserve delicate impressions around parts of the Concavenator skeleton. Rapid burial is a plausible contributor to preservation. A fossil bed can nevertheless combine biological processes, water movement, decay and later compaction. The exceptional state of one specimen does not mean that every animal in the ecosystem is represented equally well.

The skeleton and estimated size

MCCM-LH 6666 preserves an almost complete skull, much of the vertebral column, ribs, shoulder and pelvic regions, and substantial portions of both the forelimbs and hind limbs. The reported sequence includes ten cervical, thirteen dorsal and five sacral vertebrae, as well as around thirty caudal vertebrae. Some hand and foot bones and the end of the tail are missing. The skeleton is articulated, but it remains incomplete and has passed through preservation and preparation that must be considered when measuring it.

Common reconstructions put the animal at roughly five to six metres long, with mass estimates around 300–500 kilograms. Neither number is a direct weighing or a tape measurement of an intact living dinosaur. Missing elements must be restored, and mass estimates depend particularly on the reconstructed torso volume. A compact model and a deeper-bodied model can yield different totals even when based on the same bones.

The body plan was that of a bipedal theropod, with a long tail and forelimbs that remained functional. The joints and muscle-attachment areas constrain how the limbs could move, but they do not document a precise hunting sequence. No prey animal is preserved in the skeleton's digestive tract, so its diet is inferred from its predatory anatomy and its place among theropods rather than from a known meal.

The paired high spines

The feature that made Concavenator famous lies on the back above the pelvis. The neural spines of dorsal vertebrae eleven and twelve rise to more than five times the height of their vertebral bodies. They create a narrow, concentrated peak rather than a uniformly elevated ridge along the whole back. This arrangement differs from the extended series of tall spines in Acrocanthosaurus, where the elevated profile runs across many vertebrae.

The spines are unquestionably bone. Their exact external outline in life is not. A soft-tissue hump, a localised ridge, a structure supported by connective tissue or another contour have been proposed. A thin sail is also an artistic possibility, but it is not directly demonstrated by the fossil. Display, thermoregulation or energy storage have been suggested as possible functions; the vertebrae alone cannot select among them. The preserved anatomy does not reveal how much tissue covered the structure.

This distinction matters in illustrations. A high hump may communicate the unusual vertebral profile, but a sharply defined fleshy peak is a reconstruction rather than a fossil impression. Colour, skin texture and whether the feature changed with age are also unknown. The paired spines are diagnostic evidence; a specific silhouette and use are hypotheses layered over that evidence.

Scales and the disputed forearm bumps

Impressions associated with the lower foot and tail preserve small-scale details that are rarely available for non-avian dinosaurs. They include scales and an arrangement on the foot comparable in some respects to the covering, or podotheca, of living birds. The impressions show that these particular areas were not bare bone in life. They do not establish a complete body-wide pattern or prove that every part of the animal had identical scales.

A row of small bumps on the ulna, one of the forearm bones, was initially interpreted as attachment points for feather-like structures. Similar arrangements in living birds can anchor feathers, which made the comparison intriguing. However, the bumps may instead be associated with muscles, tendons or other soft tissues. The interpretation remains contested, and no feather is preserved attached to the forearm of this specimen.

It would therefore be too strong to describe Concavenator as definitively feathered on the basis of those bumps. It would also be too strong to infer a fully scaled body from the foot and tail impressions. The evidence is local: skin impressions around certain bones and ambiguous forearm anatomy. The rest of the covering must remain open to cautious reconstruction and comparison with other theropods.

Classification and comparisons

Concavenator corcovatus is the only generally accepted species in its genus. It is usually placed among Allosauroidea, but its exact position within the group has varied between analyses. Some studies have placed it close to the base of Carcharodontosauria, while others have recovered a relationship nearer Metriacanthosauridae. A 2025 analysis linked it with Siamraptor, but the result did not eliminate all uncertainty about its deeper placement.

These differences reflect the way evolutionary trees are inferred from character matrices. Analysts compare anatomical features across sampled species; incomplete fossils, different character coding and different taxon selection can alter the preferred branching pattern. The broad identification as an allosauroid can remain useful even if the more specific branch is unresolved. A diagram showing one final, certain position would give a misleading impression of the evidence.

Some isolated teeth and a trackway have also been reported from Las Hoyas or its broader setting. They may represent theropods, but they do not carry the unique combination of features preserved in MCCM-LH 6666. They cannot automatically be assigned to Concavenator. The type skeleton remains the diagnostic basis for the genus and species.

Feeding and what fossils cannot show

As a theropod, Concavenator was a carnivore. The fossil record does not identify a particular prey species or preserve a direct meal. Las Hoyas contained aquatic and terrestrial vertebrates, but their presence in the same regional formation does not prove that this dinosaur hunted each one. Bite marks, gut contents or a direct association could provide more specific evidence; without them, hunting scenarios remain ecological inference.

Its teeth, skull and limbs inform functional comparisons, but none alone fixes its speed, bite force or preferred prey. The skeleton does not preserve a social group, parent-offspring association or evidence of pack hunting. It also says nothing direct about the animal's calls, colour or daily activity. Reconstructions of a stalking predator in a wetland are useful visual interpretations, not scenes recovered from the limestone.

Concavenator is important because one remarkably complete Spanish fossil records a distinctive theropod anatomy and rare traces of skin. Its paired high spines are real; the soft outline and function remain uncertain. Its foot and tail preserve local scale impressions, while feather interpretations of the forearm are disputed. The most accurate account keeps those conclusions separate rather than turning all open questions into a single confident portrait.