Think that we've found just about every prehistoric species that there is to find? You'd be terrifyingly wrong if you said yes. In fact, adding a new view on the diversity of some unlikely large predators that predate humans, a new fossil this week revealed another species of South American "terror birds" known as Llallawavis scagliai.

In a new study published this week in the Journal of Vertebrate Paleontology, the researchers boasted the most complete terror bird fossil ever found, with more than 90% of the skeleton left intact, the new specimen is adding quite a lot of new questions and answers to the vast fossil record on these strange predatory species. The new species, known as "Scaglia's Magnificent Bird" allowed researchers to gain new insight into understanding the sensory capabilities of these large early birds, and after they discovered the auditory regions of the skull, the voice box and a complete trachea the researchers said that they were able to indicate hearing sensitivity far less evolved than birds living today. 

"The mean hearing estimated for this terror bird was below the average for living birds" lead researcher of the study from the Centro de Investigaciones en Ciencias de la Tierra in Córdoba, Argentina, Dr. Federico "Dino" Degrange says. "This seems to indicate that Llallawavis may have had a narrow, low vocalization frequency range, presumably used for intraspecific acoustic communication or prey detection."

Though terror birds were the predominant predators in South America, during the Cenozoic Era, this is the first time that a near complete skeletal fossil has allowed for researchers to use structures to extrapolate communication or sensitivities within the group of well-studied birds. Carnivorous, flightless birds scientifically known as "phorusracids", terror birds may not have been very loud preeners, but standing at 10 ft. tall with hooked beaks, they were tactical killers. 

"The discovery of this species reveals that terror birds were more diverse in the Pliocene than previously thought" Degrange says. "It will allow us to review the hypothesis about the decline and extinction of this fascinating group of birds."

And though they have been well-studied, with ample fossils being found in the mountains of South America, the near pristine discovery of yet another species will allow researchers to continue studying not only how these birds dominated their era, but also how their genetic makeup and attributes were passed onto other birds within the fossil record. Who knows, maybe that macaw in your den may have a little "terror bird" in him as well.