Usage of "lineage" over "species"
Lineages have many levels, it is like using the word groups in some ways, they are stacked inside each other like the worlds biggest branching Russian nesting doll. All vertebrates is a lineage, all birds is another lineage, as is chickens, as is just rhode island reds. Two individuals of any earth life will always share some lineages. Lineage is not the same as clade however since they do not have to be monophyletic and usually refers to a stem line leading to a group, because of how lineage is named, it can be confusing. For instance the gorilla/human lineage could refer to basically all the great apes minus orangutans or it could refer to the sequence organisms leading to their common ancestor, or it could refer to the genetic lines to their common ancestor and back to themselves. And easy way to think of it is the outer boundaries of a lineage is not well defined. What is used to denote the lineage will help with what it is referring too. 

You have to look at context. In paleontology because it is assumed you never have a direct ancestor it is used more vaguely almost like a "stem clade", in microbiology however it will be a far more precise term referring to one or more genetic lines.  

The concept of species is misleading because people are trying to use our instinctual categorical thinking to describe a continuous series. It is like trying to define a color any category we invent to split the spectrum up will have many problems because it is not something with discrete differences.