[1][4] The toothless adults and toothed juveniles were initially thought to be different kinds of dinosaurs, and were studied separately, until it was realized they represent the same species.

[6][4] Several features of the animal, such as the small head with large orbits (eye openings), toothless jaws, and the long neck and legs, were very similar to those of the Cretaceous ornithomimid theropods, as well as the Triassic non-dinosaurian shuvosaurids, representing a significant case of convergent evolution among these three distinct groups of archosaurs.

The tip of its jaws was covered by a beak, a feature that was previously unknown in non-coelurosaurian theropods like Limusaurus (the coelurosaurs include the most bird-like dinosaurs).

The lower part of the lacrimal, the bone that formed the front margin of the eye opening, was unique in being strongly inclined forwards.

The angular bone of the lower jaw was positioned significantly forwards in relation to the hind end of the mandible, similar to other ceratosaurians.

The axis (second neck vertebra) lacked the pleurocoel (excavation) on its front end and the foramina (openings) in its neural arch that are seen in derived ceratosaurians.

It had several skull features in common with basal theropods such as other ceratosaurs and coelophysoids, but it also shared a number of traits, including the beak and the fused sternum, convergently with the later coelurosaurs.

[12] A 2016 study by paleontologists Oliver Rauhut and Matthew Carrano found Limusaurus to be more derived, grouping together with Elaphrosaurus within the abelisauroid family Noasauridae.

The only known specimen of Elaphrosaurus is missing its skull and hands among other elements, and its affinities were long unclear (it was often considered an ornithomimosaur from 1928 well into the 1990s) until the more complete Limusaurus was found.

[15] The Italian paleontologist Cristiano Dal Sasso and colleagues, in 2018, found Limusaurus to be closely related to Spinostropheus, while Elaphrosaurus occupies a more basal position.

According to this scenario, the three fingers retained by tetanurans were therefore homologous (evolutionary corresponding to) with digit I, II, and III of basal theropods, which would have implications for the evolution of birds.

This inconsistency has been a matter of debate for almost 200 years,[21] and has been used by paleornithologist Alan Feduccia to support the hypothesis that birds are descended not from theropods but from some other group of archosaurs which had lost the first and fifth digits.

[23] To explain the discrepancy between morphological and embryological data in the context of bird origins, an alternative scenario to LDR was developed by paleontologists Tony Thulborn and Tim Hamley in 1982.

[2][24] Limusaurus was initially considered as evidence for the BDR hypothesis by Xu and colleagues in 2009 due to it—and other ceratosaurians—having a reduced first digit, with these researchers hypothesizing that a similar pattern of reduction occurred among the tetanurans (the sister group of the ceratosaurians).

[2][20][32] In a 2009 response to Xu and colleague's description of Limusaurus, biologist Alexander Vargas, Wagner and Gauthier stated in 2009 that it is plausible that ceratosaurians underwent BDR independent of the tetanurans, and therefore have no bearing on the issue of avian digit homology.

[20] An ancestral states analysis (estimation of the original anatomy of a group) by Dal Sasso and colleagues in 2018 also found that the digit reduction seen in Limusaurus occurred independently from that in tetanurans.

According to this analysis, an axis shift from digit position IV to III took place at the basis of Tetanurae after the fourth finger was lost.

[4] Anatomical features of Limusaurus such as the small head with toothless jaws and long neck were interpreted as indicating a herbivorous diet by Xu and colleagues in 2009.

[2] Paleontologist Lindsay E. Zanno and colleagues found in 2011 that adult specimens of Limusaurus show morphological traits associated with herbivory that are shared with other groups of herbivorous theropods, including the Ornithomimosauria, Therizinosauria, Oviraptorosauria, and Alvarezsauroidea, along with the troodontid Jinfengopteryx.

[4] The paleontologist David A. Eberth and colleagues suggested in 2010 that the large number of Limusaurus specimens in the Shishugou Formation mud pits indicates they were either abundant among the small vertebrate animals in the area, or that the trapped individuals had been drawn there.

[1] Paleontologist Rafael Delcourt agreed in 2018 that since both Limusaurus and Masiakasaurus have been found in assemblages of multiple specimens each, this suggests these small ceratosaurs lived in groups.

[40] All known Limusaurus fossils were recovered from the Shishugou Formation, a succession of sedimentary rocks that were deposited at the northeastern margin of the Junggar foreland basin and is about 350–400 m (1,150–1,310 ft) in thickness.

[1] Contemporaries of Limusaurus in the Wucaiwan locality include the theropods Haplocheirus, Zuolong, Guanlong, Aorun, and Shishugounykus; the sauropod Mamenchisaurus; the ornithischians Gongbusaurus, Yinlong, and Hualianceratops; the cynodont Yuanotherium; the mammal Acuodulodon; the crocodyliform Nominosuchus and another unnamed crocodyliform found with the holotype specimen of Limusaurus; and the turtles Xinjiangchelys and Annemys.

According to Eberth and colleagues, the high incidence of Limusaurus indicates that the abundance of small theropods is underestimated elsewhere as these animals are generally less likely to fossilize.

The mudstones probably accumulated either in standing water or a water-saturated substrate; root traces at the top of the layers indicate a marsh-like environment.

[1] The deformation structures and the consistent size of the pits suggest that they represent the footprints of giant sauropods such as Mamenchisaurus sinocanadorum, which was likewise found in the Shishugou Formation and would have had a mass of over 20 t (22 short tons) and a limb length of over 3 m (9.8 ft).

The third pit, TBB2005, contained twelve Limusaurus individuals, including the holotype, but also the tail of a small ornithischian dinosaur as well as two crocodyliforms, two mammals, a turtle and three tritylodontid cynodonts.

These observations led Eberth and colleagues to conclude that the skeletons must have accumulated within the mud pits over an extended time span rather than during a short-term death event.

The neck and tail of one specimen are bent upwards, suggesting that the carcass was pushed down towards the bottom of the pit by trampling of another animal that became trapped at a later time.

Eberth and colleagues found it likely that the burial of all individuals occurred in less than a year, based on the seasonality of the local climate and the similarity of the sediments of the three pits.