This is something I have in mind for my Visions of Empire setting(s). The idea came to me when I was trying to imagine what the society of sentient Tokay Geckos will look like. The end result is quite different from a gecko, but similar in certain terms...
These are the Cicek - bipedal, though horizontally-oriented (think modern representation of theropods) warm-blooded reptilian-equivalents. Their ur-species predecessors were pouncers, mostly carnivorous though technically omnivorous, of approximately 100kg (200 pounds) each in weight, about 2 meters in length, balancing tail included. The body is covered with scales (color ranges from green to reddish-yellow depending on morph), and the jaws and teeth are well-developed for killing prey and tearing its flesh. They are originally grassland dwellers, and do not climb well, but spread into lightly forested areas as well before achieving full sentience.
Cicek show strong sexual dimorphism - the female is about 75kg and much smaller than the 100kg male. The overriding social instinct of the ur-species were highly different between males and females. Females were social, tolerated each other and cooperated in hunting, while males were highly antagonistic towards each other, and highly territorial, trying to kill and each other at sight. When climatic change and the introduction of larger prey into their habitat forced them into social units larger than a single male and his harem of several females, the males had to conquer their instinctive antagonism towards each other in order to cooperate. So Cicek culture, especially in regard to males, revolves around mitigating this aggression, though very elaborate and highly ritualized systems of politeness and honor which have evolved during early sentience in order to prevent cannibalism between the males of the same tribe. Despite all of this, even the modern Cicek male sees all other males as rivals; culture teaches him how to channel this rivalry into (usually) non-lethal avenues, such as competing for honor and (usually) non-lethal duels, but, at his most basic impulse, he is full of aggression towards any other male.
Female and male social systems work differently. Male social organization is hierarchical, with the weaker male submitting to the stronger male, while all the time looking for an opportunity to best him and take his place, while the dominant male sees his subordinates both as a resource and a threat. This is not just a physical competition, but also a social one; if a subordinate gains significantly more honor than his superior, he will replace him, possibly without a serious fight. Female society, on the other hand, is far less competitive, and far more egalitarian: a female sees her female tribe-mates as sisters, not as rivals. Females think of the good of their tribe and only then of their own good; males think of their own position in the ever-changing hierarchy and only then of the good of their tribe. Even today, Cicek possess somewhat differentiated economic and social systems for both sexes, competitive for males and cooperative for females.
The Cicek led, until relatively recently (several centuries before the current timeline), a TL1 tribal existence on their homeworld, bound into tribes of a few thousand Cicek each, possessing primitive metalworking techniques and agriculture based on herding. But then the Reticulans came - aliens who'd rather see others fight for them, than fight themselves; and, to them the 100-kg Cicek male, in all his predatory might and temper to match, looked like a great shock-trooper to fight Reticulan wars. So the Reticulans uplifted the Cicek, providing high-tech weapons and equipment to friendly tribes in return for recruiting Cicek mercenaries to fight for the Reticulans. This had a profound impact on Cicek society. While other species, such as Humans and Reticulans, have gone through millennia of cultural evolution to support more and more complex social forms and collective identities, the Cicek have received modern technology ready-made without all of this. Culturally, the Cicek are still strongly tribal, and have difficulties to form any higher collective identity - concepts such as "nation" or "Cicek-Kind" mean little to them, despite the fact that both Reticulans and Humans tried to introduce them into Cicek society. The modern Cicek is typically very loyal to his or her tribe, but feels very little affinity to any larger body of Cicek or even to the whole species. The introduction of modern technology also meant that within a few years, almost all tribes on the Cicek homeworld were using tanks and plasma guns to fight wars which, only a short while before that, were fought using bronze axes and composite bows. The homeworld became a very dangerous place indeed... So many Cicek tribes were quick to put their hands on starships (bought from Reticulan traders) and emigrate to far-away stars. The tribal nature of the whole affairs also meant that very soon, the Reticulans had only partial control over the Cicek tribes, as each tribe has its own independent will. Soon enough, Cicek mercenaries and pirates became very common all over known space.