Check out this cool article about normally-solitary reptiles laying eggs in communal nests.
Communal nesting!? What's that, Alex? For one, it has traditionally been thought of as a non-reptilian behavior. Communal nesting is simply the laying of eggs by a female animal into the nest of a conspecific (same species) animal. This behavior is different than cooperative breeding, which could be thought of as a "daycare system" - individuals care for the young of other individuals, even at the expense of their own breeding abilities.
A quote that summarizes the opinions of the authors on why communal nesting occurs in some reptiles:
Building a nest can be hard work for reptiles. Some female lizards, for example, may spend days digging a hole deep enough to deposit eggs. During those days, she is not doing other important things such as finding food. She is also more vulnerable to predators. Females can avoid these costs by simply laying eggs in a nest that someone else has gone to the trouble to build.
The model, the authors argue, could be advantageous in an evolutionary sense. It is common sense to note that anything that reduce an animal's required level of energy expenditure to successfully pass on genetic material is good for the species in the long-run. This argument does NOT always hold true; however, that's the common sense approach. It is still true that parental care is not the norm in most described species behaviors THUS FAR, but read on...
While searching around for the topic, I found another well-cited article summarizing review articles (articles that synthesize scientific literature) which argues that communal nesting is probably much more common in reptilian species than first thought. If you read through the article, you note how little is known about nests in most species of reptiles. In fact, for most named species, nests have never even been reported in the scientific literature! Just another opportunity to grab your hiking boots and go outside!