Phylogenetic and paleoecological studies of early vertebrates and fossil fishes

在特殊的化石沉积物中发现的完整的鱼化石骨骼提供了丰富的信息。在我的实验室里，我们把重点放在这些沉积物上，以了解生活在志留纪和早期泥盆纪（4亿到4.3亿年前）的物种的起源、关系、生活方式和解剖学特征，当时早期有颌和无颌的脊椎动物数量众多，种类繁多。这些特殊的化石矿床位于西北地区的麦肯齐山脉和加拿大北部的其他地区。一个地方至少有60种早期脊椎动物，包括无颌动物和与鲨鱼和硬骨鱼有关的早期有颌脊椎动物。大多数都是完整的骨架。其中一些可以让我们检查骨骼的生长情况。另一些则告诉我们身体特征的进化，比如成对的鳍、牙齿、耳朵和内脏。这些研究包括与世界其他地方发现的化石进行仔细的比较，并使用现代计算机方法重建生命之树。始新世（5000万年前）的一个地方有成千上万的鱼类标本保存在每年的湖泊沉积物层中。一名来自北达科他州的研究生开创了一种新方法，通过化石鳞片和椎骨计算出了鱼类的生长速度。通过我实验室的博士后奖学金，我们将把这种方法应用于始新世地区的优秀藏品，以了解几个世纪和几千年来的气候变化对生长速度的反应。我们将把这些方法扩展到其他化石沉积物，了解鱼类的生长速度在长期气候变化期间是如何变化的。对非同寻常的沉积物的研究比对化石碎片的研究更能让我们了解已灭绝的脊椎动物。结果可以扩展到不太有利的情况。当化石物种和它们的生物学被更好地了解时，通过化石碎片来确定岩石的年代和追踪动物随时间的变化将更加可靠。鱼鳞和椎骨告诉我们古代物种的生物学，并可以预测现存物种在气候变化期间的反应。

Complete skeletons of fossil fishes found in exceptional fossil deposits yield a wealth of information. In my lab we focus on these deposits to learn about the origins, relationships, mode of life, and anatomical features of species that lived during Silurian and Early Devonian time (400 to 430 million years ago), when early vertebrates with jaws and their jawless relatives were abundant and diverse. These exceptional fossil deposits are in the Mackenzie Mountains, N.W.T. and other parts of northern Canada.    One locality contains at least 60 species of early vertebrates, including jawless forms and early jawed vertebrates related to sharks and bony fishes. Most are complete skeletons. Some of them allow us to examine growth of the skeleton. Others tell us about the evolution of body features such as paired fins, teeth, ears, and guts. These studies involve careful comparisons with fossils found elsewhere in the world and use modern computerized methods of reconstructing the tree of life.    An Eocene (50 million years old) locality contains thousands of specimens of fishes preserved in annual layers of lake sediment. A new approach pioneered by a graduate student from North Dakota reveals growth rates of fishes calculated from fossil scales and vertebrae. Through a postdoctoral fellowship in my lab, we will apply this method to excellent collections from the Eocene locality to learn how growth rates responded to climate changes over centuries and millennia. We will extend these methods to other fossil deposits, learning how growth rates of fishes changed during long-term climate change.    Study of extraordinary deposits shows us more about extinct vertebrates than study of fragments of fossils. The results can then be extended to less favorable situations. Dating of rocks by fragments of fossils and tracing of faunal changes over time will be more reliable when the fossil species and their biology are better known. Fish scales and vertebrae teach us about the biology of ancient species and can lead to predictions about responses of living species during climate change.