These are extremely rare,said Philip Donoghue, a paleontologist at Britain's University of Bristol. Studying them is a problem.
These are extremely rare,said Philip Donoghue, a paleontologist at Britain's University of Bristol. Studying them is a problem.
“它们太小了，研究它们很成问题。”巴西布列颠大学的古生物学家菲利浦·多纳说到。