As the genus name implies, Thalassodromeus was originally proposed to have fed like a modern skimmer bird, by skimming over the water's surface and dipping its lower jaws to catch prey.

[7][6] In 2006, palaeontologists David M. Martill and Darren Naish suggested that Thalassodromeus was a junior synonym of the related genus Tupuxuara, which was named by Kellner and Campos in 1988 based on fossils from the same formation.

In the view of Martill and Naish, the differences between these genera (including two species of Tupuxuara, T. longicristatus and T. leonardii) were due to ontogeny (changes during growth) and compression of the fossils; Thalassodromeus was simply an older, larger, and better-preserved individual.

They also noted that one specimen of Tupuxuara had a larger skull than Thalassodromeus (measured from the tip of the premaxilla to the back of the squamosal bone), despite Martill and Naish's contention that the latter was an older individual.

[7] Palaeontologists Jaime A. Headden and Herbert B. N. Campos coined the new binomial Banguela oberlii, based on their reinterpretation of the jaw tip as belonging to a toothless member of the family Dsungaripteridae, in 2015.

[6] In 2020, palaeontlogist James McPhee and colleagues considered Banguela a valid genus, and instead classified it as a member of the family Chaoyangopteridae, and did not find a dsungaripterid identity well-supported.

[12] In 2015 palaeontologists Gerald Grellet Tinner and Vlad A. Codrea named a new species, T. sebesensis, based on what they interpreted as part of a cranial crest in a concretion found near the Sebeș River in Romania.

[13] Palaeontologist Gareth J. Dyke and a large team of colleagues immediately rejected the pterosaurian identification of the T. sebesensis fossil, instead arguing that it was a misidentified part of a plastron (lower shell) of the prehistoric turtle Kallokibotion bajazidi (named in 1923).

[1][6][3] Although the postcranial skeleton of Thalassodromeus is unknown, relatives had unusually short and blocky neck vertebrae, with well-developed front and hind-limbs that were almost equal in length (excluding the long wing-finger).

[1][6][3] Despite its size, the crest was lightly built and essentially hollow; some areas indicate signs of skeletal pneumatisation and a well-developed trabecular system uniting the bones.

[1][3] A small, 46 mm (1.8 in) opening was present above the orbit (eye socket), piercing the basal part of the crest; such a feature is unknown in other pterosaurs, and does not appear to be due to damage.

[6][3] The palatal area at the tip of T. sethi's snout was a sharp ridge, similar to the keel seen on the upper surface of the mandibular symphysis where the two halves of the lower jaw connected.

[17] Martill and Naish considered Tapejaridae a paraphyletic (unnatural) group in 2006, and found Tupuxuara (which included Thalassodromeus in their analysis) to be the sister taxon to the family Azhdarchidae.

According to Martill, features uniting members of Neoazhdarchia included the presence of a notarium (fused vertebrae in the shoulder region), the loss of contact between the first and third metacarpals (bones in the hand), and very long snouts (more than 88% of the skull length).

The ability to control its body temperature would have aided Thalassodromeus during intense activity (such as hunting), and they suggested that, when in flight, heat would have been dispelled more effectively if the crest were aligned with the wind, while the head was intentionally moved to the sides.

Kellner and Campos posited that the crest could have had additional functions, such as display; aided by colour, it could have been used in species recognition, and could also have been a sexually dimorphic feature (differing according to sex), as has been proposed for Pteranodon.

They deemed the thermoregulation hypothesis an unlikely explanation for the blood-vessel channels on the crest, which they found consistent with nourishment for growing tissue (such as the keratin in bird beaks).

Hone, Naish, and Cuthill suggested that the wing membranes and air-sac system would have been more effective at controlling heat than a crest, and wind and water could also have helped cool pterosaurs in high-temperature maritime settings.

He found the idea that the crests were used for thermoregulation problematic, since they did not grow regularly with body size; they grew at a fast pace in near-adults, quicker than what would be predicted for the growth of a thermoregulatory structure.

They argued that Thalassodromeus would have fed in a similar way, as implied by the genus name; skimmers skim over the surface of water, dipping their lower jaw to catch fish and crustaceans.

Conceding the difficulty of reconstructing Thalassodromeus's fishing method, they envisioned it with a less-mobile neck than skimmers; with the crest impeding its head from submersion it would glide, flapping its wings only occasionally.

They found that its well-developed jaw muscles differed from those of the possible dip-feeder Anhanguera and the terrestrially stalking azhdarchids, indicating that T. sethi had a strong bite force.

[29] In 2018, Pêgas and colleagues agreed that Thalassodromeus' blade-like, robust jaws indicated that it could have used them to strike and kill prey, but they thought that biomechanical work was needed to substantiate the idea.

[6] In a 2002 comment on the original description of T. sethi, engineer John Michael Williams noted that although Kellner and Campos had mentioned that the large crest might have interfered aerodynamically during flight, they had not elaborated on this point and had compared the pterosaur with a bird one-fifth its size.

Williams speculated that the crest would be inflatable with blood and presented varying air resistance, which he compared to a handheld fan; this would have helped the animal change the attitude of the head during flight (and during contact with water), keeping it from rotating without powerful neck muscles.

The crest would have made long flights possible, rather than interfering; Williams compared it with the spermaceti in the head of the sperm whale, stating it is supposedly used to change buoyancy through temperature adjustment.

Kellner and Campos rejected the idea of an inflatable crest, since its compressed bones would not allow this; they did not find the sperm-whale analogy convincing in relation to flying animals, noting that spermaceti is more likely to be used during aggression or for sonar.

The enlarged shoulder muscles may have allowed them to accelerate quickly when running, and they may have been as adapted for movement on the ground as has been suggested for azhdarchids; Witton cautioned that more analysis of thalassodromids was needed to determine this.

[32] Other pterosaurs from the Romualdo Formation include Anhanguera, Araripedactylus, Araripesaurus, Brasileodactylus, Cearadactylus, Coloborhynchus, Santanadactylus, Tapejara, Tupuxuara,[33] Barbosania,[34] Maaradactylus,[35] Tropeognathus,[36] and Unwindia.

[31] Well-preserved fish fossils record the presence of hybodont sharks, guitarfish, gars, amiids, ophiopsids, oshuniids, pycnodontids, aspidorhynchids, cladocyclids, bonefishes, chanids, mawsoniids and some uncertain forms.